OVirt
oVirt is a free platform virtualization management web application community project started by Red Hat. oVirt is built on libvirt which could allow it to manage virtual machines hosted on any supported backend, including KVM, Xen and VirtualBox. However, oVirt is currently focused on KVM alone. oVirt is an open source software with backing from Red Hat and it is the base for Red Hat Enterprise Virtualization.
Read more about Ovirt.