From KDE Project announcement page, "...The KDE Project today announced the immediate availability of KDE 3.5.4, a maintenance release for the latest generation of the most advanced and powerful free desktop for GNU/Linux and other UNIXes. KDE now supports 65 languages, making it available to more people than most non-free software and can be easily extended to support others by communities who wish to contribute to the open source project..."
Read more for new significant enhancements at kde.org...
BTW, I am running KDE 3.5.3 :)
$ kdesktop --version
Qt: 3.3.6 KDE: 3.5.3 KDesktop: 3.5.3
Binary packages and source code are available for free download from KDE's download server at http://download.kde.org.