Virtualization

I don't want to use Hyper-V because it requires a separate machine (unless you're developing on Windows 2008 -- I'm not).
I don't want to use Virtual PC because it doesn't support snapshots.
I don't want to use VMWare player because it doesn't have a good api.
I don't want to use VMWare server because it just plain sucks.
I don't want to use VMWare Workstation because it isn't free.
I am using VirtualBox. It has snapshots. It can be automated with a very rich command line.

For Example:

.\vboxmanage guestcontrol execute [[TheMachineName]] \\vboxsvr\Public\InstallStuff.exe --username [[theUserName]] --password [[thePassword]]

Automatically installs the latest build of the software. InstallStuff.exe is an AutoHotKey script that gets the latest build from a network share then automates the installer. So this automates the deployment of the latest build on a virtual Machine.