I just would like to add <http://www.miwie.org/tex-refs/> to the sources
already mentioned. Unfortunately, Michael Wiedmann seems to have stopped
working on his "References for TeX and Friends". The source is written
in DocBook/XML, and I think it's still the most recent source available
for a project like this, apart from the much older LaTeX online help.

Regards,
Jürgen.