Since I spend a lot of time in Photoshop, I'm always on the lookout for new brushes, vintage photos, fonts and textures. Here are some of my favorite sites to pick up fabulous brushes. They're FREE.
The brushes I turn to on almost a daily basis are Jason Gaylor's gorgeous high-resolution brushes at DesignFruit. You can pick up the brushes for free or buy his high-res vector images at very reasonable prices.
Jason Gaylor's Tasty Tattoo Brushes.
For sheer beauty, Anika Von Holdt's brushes cannot be beat. Featuring angels, ghosts, cemeteries, and other gothic subjects, these brushes are detailed and delightful. You can find them at The Fifth Muse.
Another great site for both brushes and vector art is BittBox. The site offers very generous terms and conditions, allowing you to use these in works you plan to sell.