The Xubuntu Development and QA teams use several PPAs (personal package archives) for staging, testing and previewing new packages and package versions. These PPAs can be found under the Xubuntu Developers page on Launchpad. The current official PPAs for development and testing use are below.
https://launchpad.net/~xubuntu-dev/+archive/ubuntu/staging
The staging PPA for Xubuntu QA. The packages and package versions in this PPA can be found in the current development version of Xubuntu and are available for use with the latest stable version.
https://launchpad.net/~xubuntu-dev/+archive/ubuntu/experimental
The experimental PPA for Xubuntu QA. The packages and package versions in this PPA may be found in a later version of Xubuntu. Packages that have passed verification and will be included in the next stable version of Xubuntu will be moved to the Staging PPA.
https://launchpad.net/~xubuntu-dev/+archive/ubuntu/sru-staging
The staging PPA for Xubuntu stable release updates (SRU). The packages and package versions in this PPA are being prepared for inclusion in a supported version of Xubuntu.
https://launchpad.net/~xubuntu-dev/+archive/ubuntu/extras
The preview PPA for Xubuntu. The packages in this PPA are considered for inclusion in the Ubuntu repositories and/or Xubuntu at a later time. The packages in this PPA have not undergone significant testing and are not guaranteed to be included in a later release.
https://launchpad.net/~xubuntu-dev/+archive/ubuntu/xfce4-gtk3
This PPA includes Xfce components built with GTK+ 3 support. As components are released with GTK+ 3 support, they are included in this PPA.