I've made about $1,000 selling to istockphoto.com.
The last poster is correct - I have about 30,000 good stock photos, but only about 300 on istockphoto. They are absurdly picky and reject most of my spectacular photos with little or no reason. The don't allow photos with lense flare, motion blur, dogs, building architecture, logos of any kind, people without model release, etc. I spend many hours uploading and editing to get that $1000, not worth it. I even had a GREAT photo rejected because there was a bottle in the photo shaped like a Coke bottle.