eCos (Embedded Configurable OS) is an open source, configurable, portable, and royalty-free embedded Real Time Operating System. It is written in C++, provides all the usual OS things. You configure the OS so that the parts you don't need aren't loaded to the embedded system. eCos is released under a modified GPL that allows for its use in embedded systems without having to GPL the embedded application.
SoL (Server optimized Linux) is a Linux distribution completely independent from other Linux distributions. It was built from the original source packages and is optimized for heavy-duty server work. It contains all common server applications, and features XML boot and script technology that makes it easy to configure and make the server work.
openMosixLOAF (openMosix Linux-On-A-Floppy) is a single floppy openMosix Linux mini-distro designed for harddiskless systems or HPC clusters where only CPU and memory is needed. It has drivers for all PCI Ethernet NICs that the Linux kernel has support for (10/100/1000) and comes on only one bootable 1.6MB 3½" floppy diskette, ready to be a node in your HPC cluster.
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.