In general there are two flavors of X desktop. The two most famous "heavyweight" desktop projects are GNOME and KDE; these include both a desktop environment and an application development framework. A desktop environment includes a window manager, help browser, file manager, task bar, and so on. A development framework includes any number of libraries to ease application development, perhaps most importantly a GUI toolkit. GNOME and KDE are the desktops with the most support from Linux distribution vendors.
The second flavor of X desktop includes a desktop environment only; no development framework is included. The line between this flavor of desktop and a plain old window manager is a bit blurry; many people would describe Xfce, WindowMaker, and Enlightenment as desktops in this category.
Desktops can be mixed-and-matched; for example, you can run Enlightenment together with GNOME or KDE components; you can run applications developed with the GNOME or KDE development framework under any of the X desktops. One purpose of freedesktop.org is to ensure that this mixing-and-matching remains possible, and promote more of it. Read our Mission Statement for details. The executive summary is that people or organizations developing applications do not need to worry about which desktop their users will select. Applications which work with any desktop are easy to write.
One way to think about the mission of freedesktop.org is this: to ensure that the different development frameworks aren't user-visible.
X Desktops with a Development Framework
- Backbone: A GNUstep-based desktop environment
- Étoilé: another GNUstep-based Desktop Environment
- GNOME (developer site): The GNU Network Object Model Environment
- GNUstep: The GNU OpenStep Implementation
- KDE (developer site): The K Desktop Environment
- Unity: A desktop environment built on GNOME
Plain Desktop Environments
- AfterStep: Window manager that combines flexibility with elegant look
- AntiRight: Lightweight scripted environment that uses the GTK+ toolkit
- awesome: Highly configurable, next generation framework window manager
- EDE: small desktop environment, built to be simple and fast
- Enlightenment: The Enlightenment Window Manager
- fluxbox: Lightweight WM with support for tabs
- FVWM: An extremely customizable window manager and some desktop applications
- GoFun: Lightweight Desktop Entry Specification based desktop
- IceWM: Window manager designed to be small, fast and lightweight
- LxDE: provide a new desktop environment which is lightweight and fast
- Matchbox: Environment for non-desktop systems, such as handheld computers
- MATE: MATE Desktop Environment is the fork of GNOME2
- ROX: ROX is a free, GTK+-based, fully drag-and-drop desktop
- UDE: attempt to create new WM with original Look'n'Feel
- WindowMaker: Window manager intended to work with GNUstep
- Xfce: Lightweight GTK+-based environment
- XPde: A Windows XP-like desktop environment designed for Windows users migrating to Linux
3D Desktop Environments
- Compiz: OpenGL-based 3D window manager to extend existing desktop environments like Gnome and KDE
- Metisse: Metisse 3D Desktop project
- True3D*Shell: open source 3D desktop environment