I just recently stumbled upon an excellent stock photography website.
It's called Fotolia and it offers outstanding photographs for as little as $1 (for the low-resolution version)!
Thee photos are outstanding, completely royalty free and, with few limitations, can be used as much as you want within your materials. I recently used a bunch of them for a customer of mine, Expression Of Life Chiropractic. THe images are simply stunning and would cost thousands of dollars if you attempted to stage these images yourself.
One of the best things about Fotolia is the search engine. Not only is there extensive category and keyword information, but they show you pictures within the same group as well as with the same model. They even have a way to put in a color and get pictures that match the color!
All this for just $1 a picture! (High resolution versions aren't much more anywhere from $2 to $5).
Definitely check Fotolia out.