EveryStockPhoto
A photo search engine I started using when yotophoto shut down. I really miss yotophoto and wish they would come back. Searches my favorite free stock photo places like sxc and imageafter.

PhotoEverywhere
Nice travel photos from around the world.

PD Photo
PDPhoto.org is a repository for free public domain photos. However the photos may not be high-res. Better resolution images are apparently available for a small fee.

openphoto.net
Free stock images. A little hard to use. Look for the image url or the Raw Image link after clicking download.

Blue Vertigo: Massive Graphics Resource List
The website is slightly disorientating, hence the word "Vertigo", but you can find free and paid stock photos, fonts, PS brushes, vector graphics, color tools, sounds, patterns, and textures from the listing as you scroll - to the right.

MrNifty: 100 Legal Sources for Free Stock Images

PhotoRack
Free Stock Photo Images "Terms of Use: All pictures listed at PhotoRack are Free to use for personal and commercial projects. No limitations. No backlink required to use them, however we really appreciate it if you want to link back to us."