Linux with XFree86 supports the KDE, GNOME, and commercial CDE desktop environments, and extended window managers like WindowMaker. Each uses a different set of libraries and provides varying degrees of MS Windows-like look and feel.
Information on KDE is available from http://www.kde.org/. The KDE environment uses the Qt graphics libraries, available from http://www.qt.org/. The desktop uses its own window manager, kwm, and provides a MS Windows-like look and feel.
The GNOME home page is http://www.gnome.org/. The environment uses the free GTK libraries, available from http://www.gtk.org/, and window managers like Enlightenment, http://www.enlightenment.org/, SawFish, http://www.sawfish.org/. There's also a Web page for GNOME installation and upgrade that functions much like Debian's apt-get utility with a friendly GUI front end. It's at: http://www.helixcode/com/desktop/.
The commercial CDE environment uses the Motif libraries and a variation of the Motif mwm window manager, dtwm, and provides a suite of desktop and session-management utilities. Several vendors have made the source code of Motif available and provided binary packages for Linux distributions. As a starting point, download and installation information is available at
A free version of Motif, called LessTiF, is available from http://www.lesstif.org/.
WindowMaker, http://www.windowmaker.org/ is a window manager that has many desktop environment-like features. It provides support for GNUstep, http://www.gnustep.org/, a clone of the commercial NeXTStep environment.