MythBuntu is a mini media center, and MythTv is a tight integration project. At a time when I had a TV and I was thinking about the media center - I was staring.
Portable Ubuntu - bubunta, working closely in Windows thanks to the Colinux kernel. For those who need the functionality of a more or less new Linux distribution without leaving WinXP.
Remote Exploit linux is a distribution kit stuffed with the latest security tools that are not even in debian. Screwdriver sysadmin.
Ubuntu studio is a distro created for editing multimedia content. More beautiful and more convenient - but for the sake of justice, I must say that having made apt-get install ubuntustudio-audio, you can get the same software package from any Ubuntu-based distribution.
PartedLive - LiveCD and disk manipulation / recovery tools. Useful and free - we throw 70M to USB and go repair the partitions.
LinuxGamers - especially nothing to say, LiveCD with a bunch of games. What usually should be collected in parts, and then set up for a long time.