PlayDeb is an unofficial project with the mission to provide the latest open source and freeware games for the current Ubuntu Linux release, in an easy to install manner.
The PlayDeb repository extends the official repositories by providing latest versions and new games. Unlike the official packages, PlayDeb packages do not have a predefined release schedule - new game versions are provided as they become available from their authors.
There is a short and limited testing phase instead of a full testing cycle to ensure packaging quality, however it is less strict than Ubuntu's official requirements.
You may also be interested on the UbuntuBackports project. It has a limited scope compared to PlayDeb but the advantage of being an Ubuntu official project.
PlayDeb Site: http://www.playdeb.net/