- Cassandra: Welcome to your new Wikidot site
- Cassandra: A Structured Storage System on a P2P Network in Launchpad
Both sites are empty as of now, but it looks like they're planning on releasing the source some time soon using bzr for version control.
Another interesting Facebook project is Hive, a sort of data warehousing solution built on Hadoop. They've been discussing open sourcing this for several months now, but it looks like things are starting to happen with HADOOP-3601: Hive as contrib project.
On the non-Facebook open source front, we've got some news coming soon as well. We've made the decision to open source several of our internal tools under an MIT license - hold tight for more info.