ThinkUp is a free, open source web application that captures your posts, tweets, replies, retweets, friends, followers and links on social networks like Twitter and Facebook.
With ThinkUp, you can store your social activity in a database that you control, making it easy to search, sort, analyze, publish and display activity from your network. All you need is a web server that can run a PHP application.
via http://education.zdnet.com/?p=2417 "Like Twitter, it’s a microblogging site, but it builds in significant additional functionality to support classroom interactions." "When you create an account, you designate yourself as a teacher or student. Teachers can create groups that students join when they create their accounts (students can join multiple groups and teachers can create and/or join multiple groups); when a group is created, the site generates a group code that must be entered to join. Then, messages, files, links, and assignments can be sent to whole groups."
Web2.0 is a term used loosly to describe a set of technologies, and their usage patterns, which shift the focus of user activity on the web from consumption to participation.