I am sure that there are bunch out there, but the one that I have found the best quality and the largest selection has to be http://veer.com I think you will find it hard to locate a better source than this one.
I always like to go to flickr and look for creative commons photos. If you just search for creative commons you should find some stuff. You'll usually have to link back or site your work but you can see the different levels to which these images are copyrighted and often edit them and such.
Thanks for all the very helpful replies. I have found that using google image and searching for ones with re-use rights offers some very decent images.
I usually use Google for images.a lot of sites are available online but they are not free,do write if you know about any site which is totally free. Home Based Jobs