While working with VirtualBox in Ubuntu 11.10 (Oneiric Ocelot), I was unable to install the VirtualBox Guest Additions. It seems this is not installed with the default installation package. VirtualBox will give you a dialog to download the ISO file but the URL is not valid for the ISO.
After some quick Googling I found the download. Ubuntu installs version 4.1.2 of VirtualBox…