A few months ago, I wrote an article on "Using Ubuntu cloud-images without a cloud". That article showed how to do this with kvm. Virtualbox is another virtualiztion technology that is especially popular on Mac and Windows. So, I figured I'd give the same basic article a try, but using virtualbox rather than kvm.
I used 'virtualboxmanage' and 'virtualbox' here, but I'm sure the same can be accomplished via the virtuabox gui, and probably similar commands to do the same thing on Mac/OSX or windows.
So, below is roughly the same thing as the kvm post but with virtualbox. Also to verify function, I did this on Ubuntu 12.04 host with Ubuntu 12.04 guest, but later versions should also work.