Via djp at the linuxcaffe here are a list of someone's Top Fifty Atheist T-Shirt and Bumper Sticker Aphorisms.

Among my favourites:

If God Wanted People to Believe in Him, Then Why Did He Invent Logic?

Viva La Evolución!

That are some that are rather more unsavoury (but hilarious) that don't bear posting here. But #1 and #16 are relevant to Rolf's post about a Brampton Church sign, and the comments on that post ;)