Everybody's favourite FOSS VM has now released as ver.3 (not my personal choice, but this is dead easy for laymen use)
Available for windows, Mac & GNU/Linux
So if you need a virtualisation of a windows machine on your mac or linux system to play games, or want to take Ubuntu for a test-drive without affecting your existing system, this should do nicely.
Support 3D video abstraction, so games & advanced video are a go.
Would suggest chjecking that your CPUis VT-capable to get best performance out of it