Finding images for various projects can be quite the challenge. Robin Good, provides a very good list of resources on his blog. Most are free for both commercial and non-commercial use.

http://sxc.hu/
http://www.morguefile.com/archive/
http://www.pixelperfectdigital.com/
http://www.openphoto.net/
http://www.imageafter.com/
http://www.stockvault.net/