Today KDE announces the release of the KDE Software Compilation 4.4, "Caikaku". The new release brings major new technologies, including social networking and online collaboration features, a new netbook-oriented interface and infrastructural innovations such as the KAuth authentication framework.
According to KDE's bug-tracking system, 7293 bugs have been fixed and 1433 new feature requests were implemented.
You can check out the Visual Guide To KDE Software Compilation 4.4 for more details on the improvements in 4.4.
As it has just been released, it is not yet available for most distos as of now.