finding good textures

hi all this isnt really a unity question but is a huge part of it. i was just wandering where i can get some textures or photos from online, which are free and dont have to mention them.

obvisouly i will anyway but its hard to keep track of what i use and i dont want to be writing a 1000 names to credit if i dont even end up using them.

so as this is a big part of any game i was just wandering if anyone knows of any good sites, i currently use stock.xchng