LaTeX's labelling mechanism is designed for the impersonal world of the academic publication, in which everything has a number: an extension is necessary if we are to record the name of things we've labelled. The two packages available extend the LaTeX sectioning commands to provide reference by the name of the section.
The titleref package is a simple extension which provides
the command \titleref; it is a stand-alone package - don't use it
in a document in which you also need to use hyperref.
The byname package is part of the smartref bundle and works well with smartref, and works (to an extent) with hyperref, but the links it defines are not hyperlinks.
The memoir class incorporates the functionality of titleref, but doesn't work with byname (though a search of comp.text.tex on groups.google.com will find a patch to byname to remedy the problem).
The hyperref bundle includes a package nameref, which will work standing alone (i.e., without hyperref: of course, in this mode its references are not hyperlinked). If you load hyperref itself, nameref is automatically loaded. Memoir requires the memhfixc when running with hyperref; however, following the sequence
\documentclass[...]{memoir}
...
\usepackage[...]{hyperref}
\usepackage{memhfixc}
nameref commands may be used in a memoir document.
Each of the name-reference packages defines a reference command
with the same name as the package: \titleref, \byname and
\nameref. The nameref package also defines a command
\byshortnameref, which uses the optional 'short' title argument
to the chapter and section commands.
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=nameref