The "
Comprehensive symbol list", lists
the symbol commands \textcopyright,
\textregistered and \texttrademark, which are available in
TS1-encoded fonts, and which are enabled using the
textcomp package.
In fact, all three commands are enabled in default LaTeX, but the
glyphs you get aren't terribly beautiful. In particular,
\textregistered behaves oddly when included in bold text (for
example, in a section heading), since it is composed of a small-caps
letter, which typically degrades to a regular shape letter when asked
to set in a bold font. This means that the glyph becomes a circled
"r", whereas the proper symbol is a circled "R".
This effect is of course avoided by use of textcomp.
Another problem arises if you want \textregistered in a
superscript position (to look similar to \texttrademark).
Using a maths-mode superscript to do this provokes lots of pointless
errors: you must use
\textsuperscript{\textregistered}
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=tradesyms