Created and run by Brady Erickson, a film and TV artist based in the Bay Area, Texturelabs is a free library of original textures covering paper, film grain, grunge, fabric, concrete, metal, atmosphere and more. All assets are photographed or created by Erickson, clearly licensed for commercial use, and available in multiple resolutions. The site also includes tutorials and custom tools for Photoshop and After Effects.
For motion design students, the paper, film and grunge categories are particularly relevant for composition work, style frames and title design. The kind of resource that gets used daily without much thought, which is exactly what makes it worth knowing about.