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.
As far as I could tell, the miwie stuff was basically a docbook
translation of the unofficial latex reference manual in texinfo,
originally written for 2.09 and updated by various people over the
years, most recently me -- http://home.gna.org/latexrefman.
This is the project I had in mind when I asked my question. I made
quite a few updates to it over the last couple years, so I think it is
"newer" than miwie; I added many 2.09 commands but had no luck finding
any 2e list. Hence my question. I did not have any precise
"specification" in mind.
Of course the "latexrefman" is purely unofficial, but of course if the
latex group itself has the wherewithal to maintain something along those
lines, then that would be vastly preferable :).
Thanks to everyone for the info about the command index and all else.