VirtualBox continues to flourish under its Oracle ownership. Thankfully, the core product remains open source, and its compatibility with fresh versions of distributions seems to be fast and up to date. Although it's not something I'd use for a server room, VirtualBox does a great job of emulating desktop environments.

• VirtualBox: 56.1%

• VMware: 17.7%

• KVM: 13.5%

• Xen: 5.3%

• QEMU: 3.9%

• Citrix Xenserver: 1.6%

• Other: 1.5%

• OpenVZ: .4%

• Scalent V/OE Software: .1%