foXdesktop  
   Lightweight desktop environment, uses Fox multiplatform C++ widget set. [Open Source, LGPL]
   http://foxdesktop.sourceforge.net/

Smashplay  
   Web-based desktop GUI, looks and acts like Windows and Mac OS. Using Flash so users can open a variety of programs and have control over the interface.
   http://www.smashplay.com/

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]
   http://www.xfce.org/

Alternative Linux Desktop Environment  
   Provides C++/Java application framework.
   http://sourceforge.net/projects/alde/

Hooray for Bluecurve  
   Article praises, analyses Red Hat's new user interface in their Linux 8.0. [Linux Review]
   http://www.linuxjournal.com/article.php?sid=6476

Xfce Desktop Environment  
   Runs on FreeBSD, Linux, SunOS/Solaris; English, French, German. Description, downloads, CVS, screenshots, bug reports, fora. [Open Source, GPL; SourceForge.net]
   http://sourceforge.net/projects/xfce/

The GUI Gallery  
   Surprisingly large and thorough Graphical User Interface list, with timeline, screenshots, downloads, links. Very useful resource for students of computer interfaces.
   http://toastytech.com/guis/

Future GUIs  
   News of OS, GUI, software, related hardware developments. Updates irregularly, often interesting tidbits.
   http://www.futureguis.net/

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]
   http://osnews.com/story.php?news_id=3064

GUIdebook  
   A website dedicated to preserving and showcasing as many Graphical User Interfaces as possible. Lots of screenshots and icons.
   http://www.aci.com.pl/mwichary/guidebook

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.
   http://gpe.handhelds.org/

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.]
   http://www.stardock.com/products/desktopx/

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 unificati
   http://www.xpde.com/

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.
   http://ede.sourceforge.net/

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]
   http://www.xig.com/Pages/DeXtop/CDE-GUI.html

arm0nia project  
   A group of projects that are intended to make Unix more powerful and friendly by creating a desktop environment based on plugins.
   http://arm0nia.org/