The eight sites listed below offer huge libraries of free royalty photos you can use in your projects - and most have no restrictions on the use of the photos, except that you can not sell the photos in a collection of photos for reuse.
The Commons on Flicker - a great place to find public domain images from archiving institutions around the world. According to the http://www.flickr.com/commons/usage/,
all of the images are available for reuse without any copyright restrictions.
Photogen - thousands of professionally shot stock photos searchable by category. Registered users can download and use Photogen stock photos FREE, both for commercial and personal projects. Registration is free.