Canonical has just released and announced the first beta of Ubuntu 15.10 Wily Werewolf Flavours (Ubuntu GNOME, Ubuntu MATE, Kubuntu, Lubuntu, Xubuntu and Ubuntu Kylin). All of them now available to download and install for testing.
Blackbuntu is distribution for penetration testing which was specially designed for security training students and practitioners of information security. Blackbuntu is penetration testing distribution with GNOME Desktop Environment. It's currently being built using the Ubuntu 10.10 and work on reference Back|Track.
Ubuntu 15.04 flavors have a first beta version, it now available to download and install for testing. In this release, There are only available images for Kubuntu, Lubuntu, Ubuntu Gnome, Ubuntu Kylin, Ubuntu MATE, Xubuntu and ubuntu cloud.