To a beginning Processing user, the libraries section of the Processing site can cause a "kid in the candy store" effect. I actually recommend going a little easy, working with one library at a time. But, at the same time, working with libraries really is essential to working with Processing, because Processing "core" is kept as conservative as possible. This is especially true if you’re working with multimedia. Here are the libraries I recommend for specific multimedia applications, as a starting point:

There’s been a lot of interest in using tablets with Processing, for obvious reasons — it allows Processing to be a real-time graphics tool (or graphics for generating audio, or whatever it is you want). And Wacom tablets are cheap, high-resolution inputs. The superb SuperDraw project works with tablet input.

Unfortunately, the best library for tablets has been Windows-only (works with any Java app and — very nice — with applets in a browser):

JTablet

Now, there’s a Mac alternative, which eventually will wrap JTablet on Windows so you can deploy across platforms:

libTablet 0.1

The wonderful Marcus Wendt put this together — thanks! Let me know how it goes.