VirtualBox

To install VirtualBox virtual machine engine in Ubuntu from the repositories:

sudo apt-get install virtualbox

Then add your user to the virtualbox group.

In case you can not start the Virtual Box machines and get a message that you should install ...modules... package, try sudo apt-get install "the-corresponding-module-package". If you can not find the package in the repository (I could not find virtualbox-ose-modules-2.6.24-25-generic while running 2.6.24-25 Ubuntu kernel version), try the following:

sudo apt-get install virtualbox-ose-source module-assistant
sudo module-assistant auto-install virtualbox-ose-source
sudo /etc/init.d/vboxdrv start