While KVM is generally the de facto open-source Linux virtualization method, the Linux Foundation has announced today it will be backing the Xen virtualization project in the form of hosting it as a new collaborative project.
Xen has been around for one decade now and while it was popular in the pre-KVM days, these days the Kernel-based Virtual Machine is the preferred virtualization platform of Ubuntu Linux, Red Hat Enterprise Linux, and that of many other ISVs. Xen still has a lot corporate backing and interest and is supported as an alternative in most Linux distributions, with there being mainline Linux kernel support for Xen.
The Linux Foundation is going to continue backing KVM too, but they have decided to offer itself up as the new vendor-neutral home for Xen. Citrix has agreed. The foundation will provide the infrastructure, guidance, and a "collaborative network" to the open-source project.
The announcement comes this morning from the first day of the 2013 Linux Foundation Collaboration Summit in San Francisco. There's news of this Xen becoming a Linux Foundation Collaborative Project on LinuxFoundation.org