twitter.com
If that just sounds like another silly web 2.0 name and you've never used this service, I can't blame you. This blog post purpose is want for more people to use this already 'geek' popular tool.
Partially explained in this brilliant video -
http://www.commoncraft.com/Twitter
I can't find the words to describe twitter apart from;
• Its a fantastic messaging platform
• It does not disturb you like MSN/IM
• Content not as big as an e-mail
• Doesn't require instant reply
• Gives widespread answers
• Allows for widespread questioning
• Location based
• Open - Add it to your faceboo