DokuWiki - DokuWiki is a simple to use and highly versatile Open Source wiki software that doesn't require a database.
ChatMe - Chat with people on your school campus
Banana Dance Wiki/CMS - Free open source software combining the best of wiki and CMS with community building-features.
Involvio - Increase Student Engagement On Your Campus
TiddlyWiki - a non-linear personal web notebook
Sneek - Sneek lets you see your team mates all day and start instant video chats with a single click.