I was recently exposed to twitter.com by my good friend Brad Wilson (aka The .NET Guy). This is like a blog, but simpler and more targeted at answering the question: What are you doing? You can use it from your phone, via the web or from your IM client. Here's some info from the twitter FAQ:
What is Twitter?
Twitter is for staying in touch and keeping up with friends no matter where you are or what you’re doing. For some friends you might want instant mobile updates—for others, you can just check the web. Invite your friends to Twitter and decide how connected you want you to be.
How does Twitter work?
When you send in a mobile text (SMS), Twitter sends it out to your group of friends and posts it to your Twitter page. Your friends might not have phone alerts turned on so they may check your web page instead. Likewise, you receive your friends mobile updates on your phone.
Since I'm here at TechEd and people might want to know the answer to that question, I figured it would be a good time to start "twittering". My twitter name is pprovost.