I've stumbled on some great free texture sites recently, and it occurred to me that you guys might like them too :)  They're mostly targeted at web design, but I think they'll work just as well in 3d.

• http://www.texturelovers.com/ a lot of nice photo textures here, creative commons with attribution waived
• http://www.texturevault.net/ lots of photo textures, "medium quality" is free, higher resolution for $2 or $4
• http://designinstruct.com/category/free-resources/ just a few sets of photo textures
• http://webdesignledger.com/freebies/200-beautiful-seamless-patterns-perfect-for-web-design seamless textile patterns mostly compiled from Deviant Art