Under windows 7 and steam (perhaps all win 7 installs), mods and saves live in /Users/[username]/Saved Games/Darwinia

Mods are where you would expect, /Users/[username]/Saved Games/Darwinia/mods

Perhaps the FAQ should be updated.

All the links to the modlist I've tried here are broken. If anyone has an active copy of that website, I would be interested in getting hold of it. I think the files should be hosted on these forums and perhaps also mirrored on another page, that way if another website dies, they'll still be availab...