David Torno has a new blog called MacTex, "which comes from the words macro and texture. Basically a collection of macro photography images I've taken and will be taking in the future... They may come in helpful with your artistic creations in After Effects, Photoshop or what ever tools you use, and are 100% free for private or commercial use. They are offered as 2304 x 3456 JPG with no warranties / guarantees of any kind."
Update: a wide variety of free textures are available at CGtextures.com.