The EtherPad collaboration-enabled online system is now open source. Cool. Google bought the company, the developers are joining the Wave team, and their product is now released under the Apache 2 license.
Be sure to follow the instructions (failing to set the environment variable for the path to a MySQL client JAR file produces a strange "cp -f" error that has hung up a few people trying to build the system, as reported on Hacker News). It only took about 15 minutes to download the source and build the system - simple enough.