I figured this would be useful for mappers, I found it while looking for ground textures.
http://seamless-pixels.blogspot.com/2012/09/free-seamless-ground-textures.html
Awesome find!
New Dirt!! YAY
Here are two other sites:
1. Grunge Textures (http://www.grungetextures.com/)
2. Blueprints (http://www.the-blueprints.com/) Maybe useful for modelling
There are some nice ones here too. http://www.noctua-graphics.de/english/freetex_e.htm
Otherwise I make my own.