Widget-Coders: Primp your Widget
If you are making your own widgets, you may want to take a look at this post over at Backup Brain.
Dori Smith points to a couple of useful Photoshop how-tos to help you make your Widget as purty as can be: one from Alex Edelman on Reverse Engineering the Shiny, which aims to help you make your widgets look more like the default set from Apple, and another tutorial on making aqua buttons.
While you are over there, make sure you check out her Dashboard Resources Page, too. Very useful.