KDE 2.1 was released on February 26, 2001. Read the official announcement.
For a list of changes since KDE 2.0, see the list of changes
For a high-level overview of the features of KDE, see the KDE info page
For a graphical tutorial on using KDE 2, see this tutorial page from Linux Mandrake
Meanwhile, KDE 2.1.1 has been released. It contains several bug fixes, so we encourage to upgrade to 2.1.1. This page will no longer be updated.
If you want to compile from sources we offer instructions and help for common problems in the Compilation FAQ.
There is also info on the architecture and the programming interface.