Here's a useful texture repository that popped up in a comment yesterday beneath our 'List of free texture sites' blogpost. Enjoy!
From their 'legal stuff' statement:
The stock textures and any other photographs available for download on this site are completely free and may be used in commercial or non-commercial applications. The only exception is that they cannot be redistributed commercially in their unedited form. Credit to texturemate for use of available textures is appreciated, but not required.