For those who don't have Twitter, or don't get it, I just read perhaps the best article on the subject I've seen:
http://www.nytimes.com/2009/04/14/technology/internet/14twitter.html?pagewanted=1&_r=1&ref=technology Also, if you like video, I ran across this recently as a great primer:
http://www.youtube.com/watch?v=ddO9idmax0o