Besides all the brush creators I've featured at pstogimpbrushes (who made the brushes I use most often), I thought I'd refer you to a few other various resources.
Hello, I just made a discovery and you probably know this already but there's this script @ http://www.deviantart.com/deviation/31179822/ that auto converts .jpg, .bmp, .xcf, .png, .gif
I had seen that before, but unfortunately I can only use it at work and not at home because I can't get it to work with Linux for some reason. Thanks for reminding me about it, though, because I had forgotten all about it and now I can show the link to the other people that help me convert brushes.
I'm just starting to really get into making icons, and pstogimpbrushes has been a wonderful resource. I'd be happy to help convert brushes if you still want the help.
I just wanted to let you know that I've moved all my resources, including my brushes, to rainharbour. I don't mind if you still list them as pfefferminzchen's brushes, but you should know where to look for new stuff. Sorry for any inconvenience, but I wanted my LJ to be more personal.
Works great!