Want something other than 640×480 with Ubuntu running in VirtualBox 4.3.x?
Follow these instructions.
From http://codsplaice.blogspot.com/2014/02/a-quick-post-on-how-to-get-ubuntu-1404.html
sudo apt-get update
sudo apt-get upgrade
sudo apt-get install linux-headers-$(uname -r)
sudo apt-get install dkms build-essential
Then mount the install CD image for the Virtualbox tools and install them.
cd /media/$(id -nu)/VBOXADDITIONS*
sudo ./VBoxLinuxAdditions.run
Finally install the virtualbox-guest-x11 package.
sudo apt-get install virtualbox-guest-x11