If you haven’t seen it by now, ProxMox VE is a very nice easy to use virtualization solution based on Debian Linux and KVM/OpenVZ. KVM is used to provide full virtualization where you can take an ISO and make a complete virtual server. OpenVZ is a virtual container solution which essentially provides an OS environment without the overhead of full virtualization. ProxMox has an AJAX based web GUI and is GPL. Other solutions I’ve looked at are segways into their enterprise product, so their community (GPL) version is limited.
Rather than reinvent the wheel here and write up my own tutorial, check out this one at Griffon’s IT Library!