Status of Xen on OpenBSD, IIRC misc@ said it was childs play.
Better ask status of virtualization on DragonFly
Xen: go NetBSD. Go OpenSolaris.
Or Knoppix/parallel/cluster/Xen ...
For my part, I got the free CentOS based XenExpress.
NetBSD works even on a toaster but on none of my MBs.
And still preferring VMWare over all.