GeeXboX is a standalone media player Linux distribution, similar to MoviX. It's a small bootable CD that allows you to play your favorite video (DivX, XviD, H.264, MPEG 1/2, VCD, DVD, OggMedia, Windows Media, RealMedia, etc.) and audio (MP3, Audio CD, Ogg Vorbis, FLAC, MPC, etc.) files. It also supports networking, and is able to play media from Windows/Samba share, NFS, UPnP A/V Media Servers, RTP/RTSP servers, or SHOUTcast. It supports TV-out, TV tuners, DVB cards, and WiFi cards. It is based on MPlayer, and can be used on any x86, x86_64, or PowerPC computer. It's easy to modify the source to build your own GeeXboX or use an alternative boot method.
Source Ruckus Linux is an embeddable, robust Linux meta-distribution. It's a collection of build tools, source packages, scripts, and documentation all ready to be built into a Linux distribution. It can be used out-of-the-box, but its real strength lies in being used as a base for your own distribution. In other words, it exists purely to be forked, although it can be used as-is.
A.M.I.C.U.S. (Automatic Multimedia Installation Configuration Utility System) helps users quickly and easily install and configure MythTV on generic PC hardware. It uses the Debian Netinst CD to install GNU/Linux and just the required packages to allow a functional MythTV on low end hardware.