Daniel Shiffman, an associate professor with NYU's Interactive Telecommunications Program, got me into a lot of stuff I didn't think I'd care about with his textbook, The Nature of Code. It's about modeling natural systems with programming, generally, but in the process it makes a lot of possibilities in game development, artificial intelligence, the absolutely exploding world of creative coding, and beyond suddenly really clear and accessible. You should pick it up—or download it for a donation.
Part of what I like about Shiffman's approach, and what's probably a benefit of learning a language straight from the source, is that he doesn't ignore the fundamentals or offer shortcuts. This is a route to learn some programming rather than learn how to make a cool thing with some code you found. That's part of the larger point of Processing itself: a starter language, a stepping off point to something more like Java or Python or C++, though it seems like a lot of coders are perfectly content to stick with Processing.
Anyhow, the videos can all be found here, starting with the intro above. Together they probably amount to a full course on the language. Have fun, learn some programming, make something pretty.