Looking to get more out of twitter? Try twhirl.
twhirl is a cool "desktop twitter client," which means, in Lauren-speak, that you don't have to go to the twitter website to tweet or see tweets from your friends. It "sits" on your desktop, and has an interface like google talk.
Other cool stuff? twhirl will shorten urls for you on the spot (like tinyurl, but it's a part of the client), and let you post pictures in twitter via twitpic. It makes using twitter a total breeze.
Also cool? I can send a direct message to my personal assistant, Sandy, without opening up my browser. By the way, Sandy is really awesome.