A new 'Unity Staging' PPA has been setup to test out Unity/Unity2D packages in Oneiric. These packages are built from trunk.
This archive contains the latest builds generated from trunk, that have passed the unit tests, but didn't pass the user acceptance (autopilot) tests yet. Unless you are a developer and know what you do here, you should probably use the "unity-team/ppa" instead.
The packages in PPA are not recommended to be used on production machine. It can leave your system in unusable state so it would be better to try it out in virtualbox or on a spare system.
Run the commands below to add the PPA (Oneiric only at the moment, Precise build can be added later):
sudo add-apt-repository ppa:unity-team/staging
sudo apt-get update
sudo apt-get dist-upgrade