Alternative Linux Desktop Environment: Provides C++/Java application framework.
arm0nia project: A group of projects that are intended to make Unix more powerful and friendly by creating a desktop environment based on plugins.
DesktopX: Extends Windows desktop to support true objects (can be anything) instead of passive icons, use one by one, or mix together to form themes; build your own desktop interface, even if not a programmer. [Stardock Corporation, Inc.]
DeXtop: GUI for Unix workstations, now runs on Linux, is Common Desktop Environment (CDE) from The Open Group, based on OpenMotif 2.2.1. Runs on all Accelerated-X brand of X servers, and other X-compliant X servers. [Commercial]
EDE - Equinox Desktop Environment: Main goals of this project are simplicity, speed, minimal memory usage (if possible), good look and fell and stability. That does not mean it will be for 8086. It's FLTK-based.
foXdesktop: Lightweight desktop environment, uses Fox multiplatform C++ widget set. [Open Source, LGPL]
Future GUIs: News of OS, GUI, software, related hardware developments. Updates irregularly, often interesting tidbits.
GUIdebook: A website dedicated to preserving and showcasing as many Graphical User Interfaces as possible. Lots of screenshots and icons.
Hooray for Bluecurve: Article praises, analyses Red Hat's new user interface in their Linux 8.0. [Linux Review]
The Definitive Desktop Environment Comparison: Compares UI and usability of several desktop environments (DEs) that are widely used, admired, reviled: Windows XP Luna, BeOS 6 (Dano/Zeta), Mac OS X Aqua, Unix KDE and GNOME. Large article with many forum comments. [OSNews.com]
The GPE Palmtop Environment: A project whose aim is to provide a Free Software GUI environment for Palmtop/Handheld computers running the GNU/Linux operating system.
The GUI Gallery: Surprisingly large and thorough Graphical User Interface list, with timeline, screenshots, downloads, links. Very useful resource for students of computer interfaces.
XFce: Lightweight desktop environment for various Unix systems, easy to use and configure, fast, XFce 3 is based on GTK+. Description, downloads, screenshots, links, credits. [Open Source, GPL]
Xfce Desktop Environment: Runs on FreeBSD, Linux, SunOS/Solaris; English, French, German. Description, downloads, CVS, screenshots, bug reports, fora. [Open Source, GPL; SourceForge.net]
XPde: A desktop environment(XPde) and a window manager(XPwm) for Linux. It tries to make easier for Windows XP users to use a Linux box. Nothing more, no clipboard compatibility between Gtk and Qt applications, no emulation of Windows applications, no unification on the widgets of X applications, just a desktop environment and a window manager. [Open source, GPL]