KDE 2.1 is a multifaceted version of the K Desktop Environment. KDE is available for many platforms and in 33 languages, with more precompiled versions to be added shortly. See also this post for a more detailed introduction.
The following versions are already available:
Caldera eDesktop: i386
Debian GNU/Linux: i386, Sparc and PPC
Linux Mandrake i586
Red Hat Linux: i386, Alpha and Sparc