Twitter is a 140 character micro blog format system similar to cell phone texting (SMS). The main site is at twitter.com and can be used to answer the question "what are you doing right now". Many people use it to send short bursts of information about something, and get answers back from their friends on the network.

Links to Higher Education uses for this product

http://jeremywilburn.wordpress.com/2008/03/04/using-twitter-for-higher-ed/
http://highered.prblogs.org/2008/02/27/question-of-the-day-should-universities-tweet/
http://chronicle.com/wiredcampus/article/2785/will-new-messaging-service-catch-on-with-professors