CrunchBang (crunchbang.org) has a great resource for Gimp users:

” I love playing around with GIMP, it’s a fantastic piece of software. I use it to design websites and web graphics. I have to admit that it took me a while to really get used to using it. I was used to using Adobe Photoshop and Macromedia Fireworks. GIMP in comparison to these seemed archaic and not too user friendly. I can see now that this is not the case and I’m glad that I persevered and continued to use GIMP. GIMP is now my friend.

Anyhow, by default GIMP comes with a rather limited set of brushes. There’s a package available from the Ubuntu repositories to install some extra brushes, however this is also a little limited. To this end, I’ve created a new package containing over 150 additional brushes for GIMP.”

Visit CrunchBang to read more information and download the brushes:  http://crunchbang.org/archives/2007/11/17/150-extra-gimp-brushes-for-ubuntu