Polls Closed so I cant vote, so Pluss 1!
This guy made two good grunge brush sets: http://akisu-sama.deviantart.com/ His second set contains a liscense clause allowing any use of BOTH sets.

The current gimp (2.6. has no Distress function that I could find, but the script linked from this page (the one on the registry.gimp.org site) works fine even on a massive image!

Very well done!