Laconica Microblogging

Laconica: "Laconica (pronounced 'luh-KAWN-ih-kuh') is a Free and Open Source microblogging platform. It helps people in a community, company or group to exchange short (140 character) messages over the Web. Users can choose which people to 'follow' and receive only their friends' or colleagues' status messages. It provides a similar service to sites like Twitter, Jaiku, and Plurk."