If you want to get lost in a wonderland of links, be sure to check out Blue Vertigo. They sell cheap stock photography, but even more cool is their list of Photoshop resources.
Just scroll along the blue horizontal nav bar at the bottom to browse a veritable candy store of goodies!
I'm still going through their link list and will pick some good resources to list in the side bar on this blog.
If you have a favorite, feel free to list it in the comments. I love the free swirly brushes from ArtFlower!