For quite a while now I use VirtualBox as the virtualization software of my choice. I've used others, but the fact that it's free is a big benefit. It's also possible to use VirtualBox from the commandline. Assume that I have a VM called 'ubuntu-server', which uses 'ubuntu' as hostname. To start the VM I do the following:

alias vbm=VBoxManage
vbm startvm --type headless ubuntu-server
ssh ubuntu

To shut the VM down you can do the following:

shutdown -H now
exit
vbm controlvm ubuntu-server poweroff

Note that I've aliased VBoxManage to vbm, so that it's a little easier to use.