Are you looking for FREE grunge photoshop brushes? I have compiled a list of resources where you can find hundreds of free photoshop grunge brushes. If you can find anymore, send the link through and it will get added to the list.
Brusheezy have a massive range of brushes which you can filter to gain access to their hundreds of FREE grunge photoshop brushes.
Bittbox have 5 sets of grunge wings providing 10 brushes in total.
The Outlaw Design Blog have a range of photoshop brushes which are free. Some of the best brushes in this post are on that blog.
We Function have a free grunge brush set holding 33 subtle grunge textures and effects. They have a lot more to offer so head over.