Susan Libertiny is the host and primary artist behind Brush Portfolio. She claims that her Photoshop brushes comes from her love of gardening, global travel, music and technology. Most of the brush collections are her own creative work. A few come from artists she respects.
This site does one thing only. It shares Photoshop brush collections. There are some interesting brushes for grunge-effects, cracks, etc.
The site has a comment system. There is also RSS syndication, so you can stay current on new brush collections.
Given that this site has just one focus and it does it very, very well . . .