VirtualBox has been my main desktop virtualization solution for the past 3-4 years. VirtualBox started out as a kind of weaker version of VMware Workstation, but VirtualBox has really improved (branched snapshots etc.) over the past few years so I really can't complain especially since it has a liberal evaluation license.
VirtualBox is pretty friendly for desktop users, and is a so-called Type 2 hypervisor, so I wondered how it would fare in terms of performance relative to Hyper-V or ESXi. Turns out not too bad.