Twitter is sweeping the Internet. If you Facebook, MySpace or use LinkedIn my guess is you know what Twitter is and how to use it. It's simple really. It's a form of micro-blogging where you can send out 140 character messages to those who "follow you". Again, like I said, simple and easy concept but very powerful and popular.
If you use Twitter check out this list of 140 add on tools to increase it's power and allow you to have more fun and get more done. Very nice list at this site.
If you don't use Twitter and are wondering what all the fuss is about run over to http://www.Twitter.com and sign up.