PSDTUTS has complied a huge list of vintage grunge-effect patterns you can use freely on your projects. The links come from many sites around the Web. All together, there are samples you can preview for 450 different patterns.

http://psd.tutsplus.com/articles/a-myriad-of-vintage-grunge-patterns-from-across-the-web

And don't forget the free collection of patterns from this site:

http://www.thelightsright.com/view/Textures