Inspired by Qbista's entry about a tidally locked world, I wanted to share a site I discovered a few months back (and I had to google for a half hour to find it again).

The site has several very well thought out and thoroughly explained planets that can support life - some of them are variations in the axial tilt of the Earth, some are terraformed extraterrestrial worlds and some are weird Earths, such as 90% of the Earth's water gone, seas and land swapped, et cetera.

I think it's a very interesting read for those of us interested in world building.

http://www.worlddreambank.org/P/PLANETS.HTM