Indicator-VirtualBox is a simple yet very useful appindicator which you can use to launch VirtualBox machines without opening VirtualBox. It works with both VirtualBox and VirtualBox-OSE.
Sure, you can create shortcuts to launch VirtualBox machines, but if you constantly create new ones, a way to automatically have shortcuts for all the virtual machines sounds much better and that's what Indicator-VirtualBox is designed to do.
Install Indicator Virtualbox in Ubuntu (Lucid, Maverick and Natty):
sudo add-apt-repository ppa:michael-astrapi/ppa
sudo apt-get update
sudo apt-get install indicator-virtualbox
To launch it, press ALT + F2 (or use Synapse) and type: "indicator-virtualbox".