http://www.cl.cam.ac.uk/research/srg/netos/xen/ — The project website of the Xen™ para-virtualization machine manager from which Red Hat Virtualization is derived. The site maintains the upstream Xen project binaries and sourcecode and also contains information, architecture overviews, documentation, and related links regarding Xen and its associated technologies.

http://www.libvirt.org/ — The official website for the libvirt virtualization API that interacts with the virtualization framework of a host OS.

http://virt-manager.et.redhat.com/ — The project website for the Virtual Machine Manager (virt-manager), the graphical application for managing virtual machines.