iStockphoto.com!!
I just joined up a few weeks ago. It requires an application process for approval, but its not that hard. Just shoot on low ISO and keep it properly exposed and focused, and you should be OK. The royalties are fairly low, but if you get enough on there you can make some real cash. It ends up turning into a bit of a lifestyle really... Shooting random things, then spending hours on end labelling and uploading.
Check me out on there... IanBJohnson is my name, photos are my game!