Some time ago, ARM Holdings presented the new virtualization extensions for its processor architecture, which are now present on some models of the Cortex family, like the Cortex-A7 and Cortex-A15. Though it’s a quite recent technology, both KVM and Xen hypervisors already support such extensions, allowing to run virtualized Guests in the same way you can already do on x86. It’s true that current SoCs (System-on-Chip) and development boards doesn’t provide a number of cores and RAM memory that invite to run a significant number of Guests on them, but these are the first steps towards stabilization of ARM virtualization, paving the way for the future server-oriented ARM processors.
UPDATE (17/09/14): Some time after writing this, I’ve replaced the QEMU repository referenced here with a clean one without the changes needed for running RISCOS. I’ve just created another repository with the proper sources: https://github.com/slp/qemu-riscos. Some time ago, while trying to get NetBSD to run on Efika MX Smartbook (I should write about that), I’ve decided that I would never do any serious OS development on a platform without a JTAG interface, or a working emulator.