This image on the left is created using the four Photoshop Grunge Brushes from set 1.
This Grunge Photoshop Brush set features a selection of different sized brushes. A good set of brushes for adding dirt or texture to an image, they can also be used to age images.
There are also lots of very large Photoshop grunge brushes available on the Photoshop CD, available to buy from this site.
Check out the main grunge photoshop brushes page for a good selection of free grunge brushes.
Photoshop Packaging Brushes - set 1 