KDE announced today that the first public beta of KDE 4.0 is now available. From the annoucement:

Now the KDE libraries are rather stable, the development focus is shifting to finishing other components of the desktop. One of the most notable components is Plasma. While the developers are pretty much ready with the infrastructure for the plasmoids, most of them are not yet shipped by default Development of those features is happening in KDE’s source code repository in the playground module. Thus, you will still see good old Kicker, KDE’s panel and taskbar when you boot up KDE 4.0 Beta 1.
Javascript support has been added to plasma, and according to its lead developer we might soon support the Mac OS X Dashboard widgets. Superkaramba applets are supported already, Opera widgets might follow soon.

It’ll be kind of neat to have a globalized widget platform, as there’s a lot of good widgets out there, but generally the ones you want arn’t for your chosen platform.

Also, the file manager portion of Konqueror has been split off and named Dolphin.

I’ve always been partial to KDE. As many times as I’ve tried using XFCE and Gnome itself, I just always find myself going back to KDE on X. You can download KDE 4.0 Beta1 in pre-compiled packages for Kubuntu (Feisty and Gutsy), openSUSE, and Mandriva.  There’s also a portage overlay available for Gentoo users, however it’s been reported to be not very stable.