There are many. There isn't any official one. Mine is
http://www.undergrad.math.uwaterloo.ca/~svanegmo/if-index.html
Yes, it's a long URL. <shrug>
At the moment, there is zilch for the sake of game programmers, and I am
hoping to change that. In the meantime, it's got a links jumpoff to other
spots that could be more helpful.
There is also, in my Web pages, a <IMHO> fancy interactive index to the
ftp.gmd.de files! It's mostly parsed file listings that contain links to
the files and any reviews I might have. It's easy to browse and download
from.
/Steve