Types:
Virtuozzo is a commercial virtualization software which includes a GUI control panel.
OpenVZ is a GPL'd version of Virtuozzo (no GUI control panel).
Xen is GPL'd virtualization software (no GUI control panel)

Control Panels:
HyperVM is a control panel for either OpenVZ or Xen software.
GPLHost is a GPL'd control panel for the Xen software.

In my opinion, Xen is the better virtualization software as it seems to use the fewest resources. As for control panels Virtuozzo is the better of the the control panels.