Choice of scalable outline fonts

If you are interested in text alone, you can in principle use any of the huge numbers of text fonts in Adobe Type 1, TrueType or OpenType formats. The constraint is, of course, that your previewer and printer driver should support such fonts (TeX itself only cares about metrics, not the actual character programs).

If you also need mathematics, then you are severely limited by the demands that TeX makes of maths fonts (for details, see the paper by B.K.P. Horn in TUGboat 14(3)). For maths, then, there are relatively few choices (though the list is at last growing). There are several font families available that are based on Knuth's original designs, and some that complement other commercial text font designs; one set (MicroPress's 'informal math') stands alone. "Free" font families that will support TeX mathematics include:

Computer Modern
(75 fonts - optical scaling) Donald E. Knuth
The CM fonts were originally designed in Metafont, but are also now available in scalable outline form. There are commercial as well as public domain versions, and there are both Adobe Type 1 and TrueType versions. A set of outline versions of the fonts was developed as a commercial venture by Y&Y and Blue Sky Research; they have since assigned the copyright to the AMS, and the fonts are now freely available from CTAN. Their quality is such that they have become the de facto standard for Type 1 versions of the fonts.
AMS fonts
(52 fonts, optical scaling) The AMS
This set of fonts offers adjuncts to the CM set, including two sets of symbol fonts (msam and msbm) and Euler text fonts. These are not a self-standing family, but merit discussion here (not least because several other families mimic the symbol fonts). Freely-available Type 1 versions of the fonts are available on CTAN. The eulervm package permits use of the Euler maths alphabet in conjunction with text fonts that do not provide maths alphabets of their own (for instance, Adobe Palatino or Minion).
mathpazo version 1.003
(5 fonts) Diego Puga
The Pazo Math fonts are a family of type 1 fonts suitable for typesetting maths in combination with the Palatino family of text fonts. Four of the five fonts of the distribution are maths alphabets, in upright and italic shapes, medium and bold weights; the fifth font contains a small selection of "blackboard bold" characters (chosen for their mathematical significance). Support under LaTeX2e is available in PSNFSS; the fonts are licensed under the GPL, with legalese permitting the use of the fonts in published documents.
Fourier/Utopia
(15 fonts) Michel Bovani
Fourier is a family built on Adobe Utopia (which has been released for usage free of charge by Adobe). The fonts provide the basic Computer Modern set of mathematical symbols, and add many of the AMS mathematical symbols (though you are expected to use some from the AMS fonts themselves). There are also several other mathematical and decorative symbols. The fonts come with a fourier package for use with LaTeX; text support of OT1 encoding is not provided - you are expected to use T1.
Belleek
(3 fonts) Richard Kinch
Belleek is the upshot of Kinch's thoughts on how Metafont might be used in the future: they were published simultaneously as Metafont source, as Type 1 fonts, and as TrueType fonts. The fonts act as "drop-in" replacements for the basic MathTime set (as an example of "what might be done").

The paper outlining Kinch's thoughts, proceeding from considerations of the 'intellectual' superiority of Metafont to evaluations of why its adoption is so limited and what might be done about the problem, is to be found at http://truetex.com/belleek.pdf (the paper is a good read, but exhibits the problems discussed in "getting good PDF" - don't try to read it on-screen in Acrobat reader).

mathptmx
Alan Jeffrey, Walter Schmidt and others.
This set contains maths italic, symbol, extension, and roman virtual fonts, built from Adobe Times, Symbol, Zapf Chancery, and the Computer Modern fonts. The resulting mixture is not entirely acceptable, but can pass in many circumstances. The real advantage is that the mathptm fonts are (effectively) free, and the resulting PostScript files can be freely exchanged. Support under LaTeX2e is available in PSNFSS.
Computer Modern Bright
Free scalable outline versions of these fonts do exist; they are covered below together with their commercial parallels.
Fonts capable of setting TeX mathematics, that are available commercially, include:
BA Math
(13 fonts) MicroPress Inc.
BA Math is a family of serif fonts, inspired by the elegant and graphically perfect font design of John Baskerville. BA Math comprises the fonts necessary for mathematical typesetting (maths italic, math symbols and extensions) in normal and bold weights. The family also includes all OT1 and T1 encoded text fonts of various shapes, as well as fonts with most useful glyphs of the TS1 encoding. Macros for using the fonts with Plain TeX, LaTeX 2.09 and current LaTeX are provided.

For further details (including samples) see
http://www.micropress-inc.com/fonts/bamath/bamain.htm

CH Math
(15 fonts) MicroPress Inc.
CH Math is a family of slab serif fonts, designed as a maths companion for Bitstream Charter. (The distribution includes four free Bitstream text fonts, in addition to the 15 hand-hinted MicroPress fonts.) For further details (including samples) see
http://www.micropress-inc.com/fonts/chmath/chmain.htm
Computer Modern Bright
(62 fonts - optical scaling) Walter Schmidt
CM Bright is a family of sans serif fonts, based on Knuth's CM fonts. It comprises the fonts necessary for mathematical typesetting, including AMS symbols, as well as text and text symbol fonts of various shapes. The collection comes with its own set of files for use with LaTeX. The CM Bright fonts are supplied in Type 1 format by MicroPress, Inc. The hfbright bundle offers free Type 1 fonts for text using the OT1 encoding - the cm-super set for use with T1 texts doesn't (yet) offer support for mathematics.

For further details of Micropress' offering (including samples) see
http://www.micropress-inc.com/fonts/brmath/brmain.htm

Concrete Math
(25 fonts - optical scaling) Ulrik Vieth
The Concrete Math font set was derived from the Concrete Roman typefaces designed by Knuth. The set provides a collection of math italics, math symbol, and math extension fonts, and fonts of AMS symbols that fit with the Concrete set, so that Concrete may be used as a complete replacement for Computer Modern. Since Concrete is considerably darker than CM, the family may particularly attractive for use in low-resolution printing or in applications such as posters or transparencies. Concrete Math fonts, as well as Concrete Roman fonts, are supplied in Type 1 format by MicroPress, Inc.

For further information (including samples) see
http://www.micropress-inc.com/fonts/ccmath/ccmain.htm

HV Math
(14 fonts) MicroPress Inc.
HV Math is a family of sans serif fonts, inspired by the Helvetica (TM) typeface. HV Math comprises the fonts necessary for mathematical typesetting (maths italic, maths symbols and extensions) in normal and bold weights. The family also includes all OT1 and T1 encoded text fonts of various shapes, as well as fonts with most useful glyphs of the TS1 encoding. Macros for using the fonts with Plain TeX, LaTeX 2.09 and current LaTeX are provided. Bitmapped copies of the fonts are available free, on CTAN.

For further details (and samples) see
http://www.micropress-inc.com/fonts/hvmath/hvmain.htm

Informal Math
(7 outline fonts) MicroPress Inc.
Informal Math is a family of fanciful fonts loosely based on the Adobe's Tekton (TM) family, fonts which imitate handwritten text. Informal Math comprises the fonts necessary for mathematical typesetting (maths italic, maths symbols and extensions) in normal weight, as well as OT1 encoded text fonts in upright and oblique shapes. Macros for using the fonts with Plain TeX, LaTeX 2.09 and current LaTeX are provided.

For further details (including samples) see
http://www.micropress-inc.com/fonts/ifmath/ifmain.htm

Adobe Lucida, LucidaSans and LucidaMath
(12 fonts)
Lucida and LucidaMath are generally considered to be a bit heavy. The three maths fonts contain only the glyphs in the CM maths italic, symbol, and extension fonts. Support for using LucidaMath with TeX is not very good; you will need to do some work reencoding fonts etc. (In some sense this set is the ancestor of the LucidaBright plus LucidaNewMath font set, which are not currently available.)
MathTime Pro
Publish or Perish (Michael Spivak)
This latest instance of the MathTime family covers all the weights (medium, bold and heavy) and symbols of previous versions of MathTime. In addition it has a much extended range of symbols, and many typographic improvements that make for high-quality documents. The fonts are supported under both Plain TeX and LaTeX2e, and are exclusively available for purchase from Personal TeX Inc. \par For a sample, see http://www.pctex.com/mtpdemo.pdf
PA Math
PA Math is a family of serif fonts loosely based on the Palatino (TM) typeface. PA Math comprises the fonts necessary for mathematical typesetting (maths italics, maths, calligraphic and oldstyle symbols, and extensions) in normal and bold weights. The family also includes all OT1, T1 encoded text fonts of various shapes, as well as fonts with the most useful glyphs of the TS1 encoding. Macros for using the fonts with Plain TeX, LaTeX 2.09 and current LaTeX are provided.

For further details (and samples) see
http://www.micropress-inc.com/fonts/pamath/pamain.htm

TM Math
(14 fonts) MicroPress Inc.
TM Math is a family of serif fonts, inspired by the Times (TM) typeface. TM Math comprises the fonts necessary for mathematical typesetting (maths italic, maths symbols and extensions) in normal and bold weights. The family also includes all OT1 and T1 encoded text fonts of various shapes, as well as fonts with most useful glyphs of the TS1 encoding. Macros for using the fonts with Plain TeX, LaTeX 2.09 and current LaTeX are provided. Bitmapped copies of the fonts are available free, on CTAN.

For further details (and samples) see
http://www.micropress-inc.com/fonts/tmmath/tmmain.htm

Two other font sets should be mentioned, even though they don't currently produce satisfactory output - their author is no longer working on them, and several problems have been identified:
pxfonts set version 1.0
(26 fonts) by Young Ryu
The pxfonts set consists of The text fonts are available in OT1, T1 and LY1 encodings, and TS encoded symbols are also available. The sans serif and monospaced fonts supplied with the txfonts set (see below) may be used with pxfonts; the txfonts set should be installed whenever pxfonts are. LaTeX, dvips and PDFTeX support files are included. Documentation is readily available.

The fonts are licensed under the GPL; use in published documents is permitted.

txfonts set version 3.1
(42 fonts) by Young Ryu
The txfonts set consists of The text fonts are available in OT1, T1 and LY1 encodings, and TS encoded symbols are also available. Documentation is readily available.

The fonts are licensed under the GPL; use in published documents is permitted.

Finally, one must not forget:
Proprietary fonts
Various sources.
Since having a high quality font set in scalable outline form that works with TeX can give a publisher a real competitive advantage, there are some publishers that have paid (a lot) to have such font sets made for them. Unfortunately, these sets are not available on the open market, despite the likelihood that they're more complete than those that are.
We observe a very limited selection of commercial maths font sets; a maths font has to be explicitly designed for use with TeX, which is an expensive business, and is of little appeal in other markets. Furthermore, the TeX market for commercial fonts is minute by comparison with the huge sales of other font sets.

Text fonts in Type 1 format are available from many vendors including Adobe, Monotype and Bitstream. However, be careful with cheap font "collections"; many of them dodge copyright restrictions by removing (or crippling) parts of the font programs such as hinting. Such behaviour is both unethical and bad for the consumer. The fonts may not render well (or at all, under ATM), may not have the 'standard' complement of 228 glyphs, or may not include metric files (which you need to make TFM files).

TrueType remains the "native" format for Windows. Some TeX implementations such as TrueTeX use TrueType versions of Computer Modern and Times Maths fonts to render TeX documents in Windows without the need for additional system software like ATM. (When used on a system running Windows XP, TrueTeX can also use Type 1 fonts.)

When choosing fonts, your own system environment may not be the only one of interest. If you will be sending your finished documents to others for further use, you should consider whether a given font format will introduce compatibility problems. Publishers may require TrueType exclusively because their systems are Windows-based, or Type 1 exclusively, because their systems are based on the early popularity of that format in the publishing industry. Many service bureaus don't care as long as you present them with a finished print file (PostScript or PDF) for their output device.

CM family collection
Browse fonts/cm/ps-type1/bluesky/
AMS font collection
Browse fonts/amsfonts/ps-type1/
Belleek fonts
fonts/belleek/belleek.zip
CM-super collection
fonts/ps-type1/cm-super (zip, browse)
eulervm.sty and supporting metrics
fonts/eulervm (zip, browse)
fourier (including metrics and other support for utopia
fonts/fourier-GUT (zip, browse)
hfbright collection
fonts/ps-type1/hfbright (zip, browse)
hvmath (free bitmapped version)
fonts/micropress/hvmath (zip, browse)
pxfonts
fonts/pxfonts (zip, browse)
tmmath (free bitmapped version)
fonts/micropress/tmmath (zip, browse)
txfonts
fonts/txfonts (zip, browse)
utopia fonts
fonts/utopia (zip, browse)

This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=psfchoice