If you're not on Twitter, you're missing... well, something very strange.
I use Facebook to connect with people I've actually met, but I use Twitter to talk to writers, agents, publishers, and various forms of the Hulk, WHO ALL TWEET IN HULK FASHION, SO HULK TALK ONLY IN ALL CAPS.
Each missive is restricted to 140 characters or less, so you're challenged to be succinct, witty, and hopefully not insane.
For example, here are some of the things I've said in the past 15 minutes or so:
If that doesn't convince you, nothing should.
Twitter: It's weird, it's awesome, it doesn't make much sense. But I still love it.