“Where To Find Great Free Photographs And Visuals For Your Own Online Articles” is a great blog entry listing 12 good stock sites. Written on April 1, it has been modified a few times, but the author does not claim it as a constantly updated resource. The comments and links on the page are also helpful:
Commercial, limited licences
http://www.123rf.com – large collection of royalty-free stock photos available via subscription. Available at a very low price. Perfect for those on tight budget.
Foto Search Stock Photography – Stock photography from over 90 vendors.
http://www.istockphoto.com – large range of user-submitted stock photography that can be downloaded for as little as $1 per image. All images are covered by a general licencehttp://www.istockphoto.com/license.php, and contacting the original image authors directly to negotiate a specific licence is not allowed via the istockphoto website.
http://www.photographersdirect.com/ an online service to help picture buyers find suitable stock photography for books, magazines, adverts, brochures, calenders or any other media.
To date, they have connected 1,093 buyers from Australia to Venezuela, with 2,910 professional photographers from Andorra to Zimbabwe and have 123,525 images online.
http://www.ifimages.com/ If Images – Royalty Free and Rights Managed images – London based stock photo agency. Searchable image library with high resolution Royalty Free and Rights Managed images available for download.
http://www.areaimage.com/main.php Areaimage, Royalty Free Stock Photography. Areaimage is a library of images, populated by a wide range of talented photographers, supplying designers with images for websites, adverts and more.