Diaspora is a privacy-aware, personally-controlled, do-it-all open source social network. Check out our project site.
Diaspora is currently going through a huge refactoring push, the code is changing fast! If you want to do something big, reach out on IRC or the mailing list first, so you can contribute effectively <3333
With Diaspora you can:
Documentation is available on our wiki
Here's how you can get a development environment up and running. You can check out system-specific guides here.
curl https://raw.github.com/diaspora/diaspora/master/script/install.sh | /bin/sh
then visit 'http://localhost:3000' in your browser.