not sure about free stock images, but istockphoto is really good and isnt expensive at all when it comes to bog standard images. You cant go wrong with them.
Stock images are so cheap now anyway...you can get high-res images for about $0.50 (US) at most of the major stock agencies. And the quality will be MUCH better than what you can get for free!
i find it hard to find stock images as well so thanks for all the suggestions it has helped me too --p
photos8(dot)com Amazing public domain free pics, in my oppinion as good as google and absolutely free for personal or commercial use.
http://www.photos8.com/ That does look like a good site! Some of the terms that I searched for came back with no results, but it does look like a good source if they have what you are looking for. I will bookmark that one. Thanks for posting.