GetDeb is an unofficial project with the mission to provide the latest open source and freeware applications for the current Ubuntu Linux release, in an easy to install manner.
The GetDeb repository extends the official repositories by providing latest versions and new applications. Unlike the official packages, GetDeb packages do not have a predefined release schedule - new software 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 GetDeb but the advantage of being an Ubuntu official project.