Just in case you missed it we now have soon-to-be official Vagrant Ubuntu cloud images thanks to Ben Howard.
Never used Vagrant before? Check out these slides to get up to speed:
Here’s the TL;DR;
sudo apt-get install vagrant vagrant box add myprecisevm http://cloud-images.ubuntu.com/vagrant/precise/current/precise-server-cloudimg-amd64-vagrant-disk1.box vagrant init myprecisevm vagrant up vagrant ssh
This will install Vagrant, get the 12.04 image, and set it up as a VM with as “myprecisevm”. There’s no need to download and configure virtualbox seperately, the package handles that for you and vagrant itself makes it so you don’t need to deal with VB directly.
While that is downloading, make sure you check out the Vagrant Getting Started.