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.
FVWM-Crystal aims to create an easy to use, pretty, but also powerful desktop environment for Linux or other Unix-like operating systems. It uses the following programs: FVWM as a window manager and "main core"; different ways to provide icons on the desktop including support for many file managers and custom commands; xterm, aterm, mrxvt, or urxvt as terminal emulators; MPD or XMMS2 as music players (there's built-in support for controlling these programs), and several other tools for different functions, like setting a wallpaper or taking screenshots.
Ion is a tiling (no overlapping windows) window manager that also has PWM-style tabbed frames which can contain multiple client windows. These features help to keep windows organized and to switch quickly between them. Ion was designed primarily as an efficient and unobtrusive window manager for users who prefer the keyboard.
FVWM is a multiple large virtual desktop window manager originally derived from twm. FVWM is intended to have a small memory footprint and a rich feature set, be extremely customizable and extendable and have a high degree of Motif mwm compatibility. FVWM is highly extensible through its module interface.
dvtm brings the concept of tiling window management, popularized by X11-window managers like dwm, to the console. As a console window manager, it tries to make it easy to work with multiple console based programs like vim, mutt, cmus, or irssi. dvtm is intended to be used where X11 isn't available or over SSH. In conjunction with dtach, it can be seen as a lightweight alternative to GNU screen.
Ratpoison is a simple window manager with no large library dependencies, no fancy graphics, no window decorations, and no rodent dependence. It is largely modeled after GNU Screen, which has done wonders in the virtual terminal market. All interaction with the window manager is done through keystrokes. ratpoison has a prefix map to minimize the key clobbering that cripples EMACS and other quality pieces of software. All windows are maximized and kept maximized to avoid wasting precious screen space.