Impossible Creatures

2 Clan - http://www.freewebs.com/ic2clan/
Provides downloads, screenshots, and a member list.

Down Right Deadly Clan - http://www.freewebs.com/rare_hunter/
Has tips and screenshots.

GRC - http://www.geocities.com/grcwebsite/
Offers hints and tips.

Impossible Creatures Center - http://www.strategyplanet.com/sigma/
News site covering iCreatures, includes forums and exclusive screenshots.

The Impossible Menagerie - http://www.geocities.com/alex_j_holt/page3.html
A modification project to create new animals.