X.Org provides an open source implementation of the network-transparent X Window System, as well as working on the standard itself.
The development work is being done as part of the freedesktop.org community, sponsored by the X.Org Foundation.
The GNOME project provides two things: The GNOME desktop environment, an intuitive and attractive desktop for users, and the GNOME development platform, an extensive framework for building applications that integrate into the rest of the desktop.
The K Desktop Environment (KDE) is a graphical desktop, a set of applications and a development platform. It is created by a community of people dedicated to create a free and user-friendly computing experience. KDE offers all necessary means to easily build all kinds of applications upon.
KDE has been around since 1996, with code change history dating back at least to 1997.
KDE is one of the biggest free software C++ project around and one of the two leaders of unix desktops.
Wine is an implementation of the Windows API on top of X and Unix. It does not require Microsoft Windows, but can use native Windows DLLs if they are available. It provides both a development toolkit for porting Windows source code to Unix as well as a program loader, allowing many unmodified Windows programs to run on x86-based Unixes.
GTK+ is a multi-platform toolkit for creating graphical user interfaces. Offering a complete set of widgets, GTK+ is suitable for projects ranging from small one-off projects to complete application suites.
GTK+ has been designed from the ground up to support a range of languages, not only C/C++. Using GTK+ from languages such as Perl and Python (especially in combination with the Glade GUI builder) provides an effective method of rapid application development.
Qt is a cross-platform application and UI framework. Using Qt, you can write applications once and deploy them across many desktop and embedded operating systems without rewriting the source code.
The xterm program is a terminal emulator for the X Window System. It provides DEC VT102 and Tektronix 4014 compatible terminals for programs that can't use the window system directly.
Xfce is a lightweight desktop environment for various *NIX systems.
Designed for productivity, it loads and executes applications fast, while conserving system resources.
Cairo is a 2D graphics library with support for multiple output devices, both raster and vector.
It focusses on high quality output at display resolutions and features an extremely easy to use API.
The KDE libraries, basis of KDE and used by many open source projects. They are based on Qt, Trolltech's cross-platform toolkit, and run on Linux, BSDs, and other Unices, as well as Microsoft Windows and Mac OS X.
Licensed under GNU LGPL, they may be used by open source and proprietary applications.
A cross-platform multimedia library designed to provide low level access to audio, keyboard, mouse, joystick, 3D hardware via OpenGL, and 2D video framebuffer.
SDL supports Linux, Windows, Windows CE, BeOS, MacOS, Mac OS X, FreeBSD, NetBSD, OpenBSD, BSD/OS, Solaris, IRIX, and QNX. The code contains unofficial support for AmigaOS, Dreamcast, Atari, AIX, OSF/Tru64, RISC OS, SymbianOS, and OS/2.
SDL is written in C, but works with C++ natively, and has bindings to several other language...
Compiz is a compositing window manager that uses 3D graphics acceleration via OpenGL. It provides various new graphical effects and features on any desktop environment, including Gnome and KDE. (Short version: Wobbly windows and stuff)
Psi is a leading instant messaging / real-time communications client for the Jabber network (using the XMPP protocol). It is cross platform, available for Windows, Mac OS X and X11 (Linux, BSD, Solaris etc.) platforms. It uses the Qt library.
It aims to be (and is famous for being) standards compliant and stable. It is also at the cutting edge of XMPP development, with several of the authors very actively involved in the XMPP standards extension process.
Mesa is an open-source implementation of the OpenGL specification - a system for rendering interactive 3D graphics.
A variety of device drivers allows Mesa to be used in many different environments ranging from software emulation to complete hardware acceleration for modern GPUs.
Mesa ties into several other open-source projects: the Direct Rendering Infrastructure and X.org to provide OpenGL support to users of X on Linux, FreeBSD and other operating systems.
awesome is a highly configurable, next generation framework window manager for X. It is very fast, light and extensible.
It is primarly targeted at power users, developers and any people dealing with every day computing tasks and want to have fine-grained control on its graphical environment.
Metacity is the default window manager for the GNOME desktop environment. Its focus is on simplicity and usability rather than novelties or gimmicks. Its author has characterized it as a "boring window manager for the adult in you. Many window managers are like Marshmallow Froot Loops; Metacity is like Cheerios."
Fluxbox is a lightweight and highly configurable window manager with pwm-like tabs.
Compiz Fusion is the result of a merge between the well-known Beryl composite window manager and Compiz Extras, a community set of improvements to the Compiz composite window manager. Compiz Fusion aims to provide an easy and fun-to-use windowed environment, allowing use of the graphics hardware to render each individual window and the entire screen, to provide some impressive effects, speed and usefulness.
xmonad is a tiling window manager for X. Windows are arranged automatically to tile the screen without gaps or overlap, maximising screen use. All features of the window manager are accessible from the keyboard: a mouse is strictly optional. xmonad is written and extensible in Haskell. Custom layout algorithms, and other extensions, may be written by the user in config files. Layouts are applied dynamically, and different layouts may be used on each workspace. Xinerama is fully supported, allowi...
Fontconfig is a library for font customization and configuration.