Graphic designers, have you come across Creative Market yet? It's an online shop full of useful goodies.
Some examples from the store: textures for adding flavor to your images. Product mockups, like the vector iMac shown above ($2)— useful for showing off websites or desktop wallpapers. Also find fonts for sale, plus a selection of templates for everything from business cards to WordPress blogs. Personally I'm most interested in the Photoshop actions. Get automated processes that turn average photos interesting, like the 42-action set below ($10).
It's a good resource to keep in mind for projects, since there's lots of stuff that will save you time. Buy something for $5 that would take you three hours to make. Or if you've already spent those hours, consider selling your own digital products over there!