lifehack.org has some ideas on how to use twitter to be more productive.
I’ve been using this tool for a week or so now (as seen on the right or here) and it’s working out nice for now. For the mac-heads out there: I found Twitterific a very nice tool to be up to date via twitter. You could, of course, also use your favorite IM-client but I prefer that nifty interface Twitterific comes with. It’s simple, works reliable and disappears – for me – 30 seconds after a new “message” has come up. So if you’re trying to get out a short message to many people at once twitter might be your tool of choice.