KNOPPIX is a bootable CD with a collection of GNU/Linux software, automatic hardware detection, and support for many graphics cards, sound cards, SCSI devices, and other peripherals. It can be used as a Linux demo, educational CD, rescue system, etc. It is not necessary to install anything on a hard disk due to on-the-fly decompression.
GNUSTEP Live CD contains a lot of software for GNUstep, a free implementation of the OPENSTEP framework (which is also directly used in Mac OS X as Cocoa). It includes excellent applications for RAD (GORM and ProjectCenter). The CD is available for i486, AMD64, Apple Mac PowerPC, and Sun UltraSPARC computers.
Sherman's aquarium is a screen saver, a GNOME panel applet, and a dock applet that provides an aquarium with fish and/or turtles. In applet mode, it can display lots of information, such as CPU load, temperatures, memory usage, and many other things. Both the applet and the screensaver are very configurable.
JoyWM (formerly known as Linux Multimedia System or LMMS) is a multimedia GUI written in Python/Pygame. It provides an easy-to-use GUI for tasks such as listening to music, watching movies, viewing pictures, and playing some games. It is appropriate for use on a TV and can be controlled with a joystick (or a keyboard if no joystick is present).