If you've read this site for any amount of time, you know I love Photoshop brushes, especially grunge-style brushes. Today I came across two sets of grunge brushes by Aramisdream, and they're spectacular.

Download set one here.
Download set two here.

Uncompress the downloaded files and move the .abr files to your Photoshop/Presets/Brushes folder. Then load them into your brushes panel in Photoshop to use. They're all large, high-quality brushes and make perfect background textures for various projects.