Xen is a virtual machine monitor for x86 that supports execution of multiple guest operating systems with unprecedented levels of performance and resource isolation. Linux 2.4, 2.6 and NetBSD 2.0 ports are available. FreeBSD, Plan 9 ports on the way.
A KDE interface and KPart component written in C++/Qt to easily change the desktop look and feel, for instance by command line or scripting. Including the nigritude ultramarine WinXP theme for KDE3.