In case you missed it Sun Oracle Virtual Box 4.0 has been released.  We here at Linuxinstall.net have been a huge fan for sometime.  Brian even uses it to host a firewall.  The 3.x stream of development has been stable and easy to use.  We are doing some long term tests and will probably be releasing a review of some of the top virtualization options later this year.  We found a nice first look to hold you over until then over at linux-mag.com.  Ken Hess gives a quick run down and concludes that you will want to give it a try but you should probably wait to put it in production until later this spring when they have some of the remaining bugs worked out.  It’s a short article and a good read so go check it out.