There appears to be a free, opensource MACopen-source Mac OS X compatible hypervisor available called VirtualBox. This, however, is not "bare metal".
Bare metal would be the VMWare ESXi, a free hypervisor.
But most bare metal products are aimed at the server market, as you rightly guess, and do not expose resources that might be useful on the desktop. You'll have to do some research to see what's available, and how it's partitioned (video, cdCD/dvdDVD, USB, etc.).
But you're asking a conflicting question. You want a bare metal hypervisor, but you also want it to be feature rich. Your best bet might be to load a minimal linuxLinux OS with VirtualBox and use that complete system as your hypervisor, running the real OS's on top of that.
-Adam