My feelings toward Twitter are... less than favourable. I'm hoping it's just a fad, but even if it is, it's indicative of an inevitable trend in everything from journalism to personal privacy.
That being said, I do follow a handful of Twitters. Without a doubt, Mystery Man on Film has one of the best, most informative and entertaining Twitters. Anyone who reads this blog who's interested in screenwriting or filmmaking (so all three of you) should also be following his Twitter.