Use Ubuntu Tweak

- Add third-party sources to install things like Google Earth, Skype, Chromium, Opera, Development Versions of Firefox and Sun's VirtualBox amongst many others!

- More cool things like Gnome and Compiz Tweaks, and Startup and Session Control.  See the full list here.

Install Ubuntu Tweak

Add key for repository:

 sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com FE85409EEAB40ECCB65740816AF0E1940624A220

Add to bottom of /etc/apt/sources.list (sudo gedit /etc/apt/sources.list):

# Ubuntu Tweak Repo
deb http://ppa.launchpad.net/tualatrix/ubuntu jaunty main
deb-src http://ppa.launchpad.net/tualatrix/ubuntu jaunty main

Install Ubuntu Tweak:

sudo apt-get update
sudo apt-get install ubuntu-tweak

Enable 3rd Party Sources

1. Click Applications -> Third-Party Sources

2. Click "Unlock" in bottom right and type your password.  Read, understand and accept the warning.

3. Select the sources you want to add.  I chose Chromium, Skype, Google and Medibuntu (leaving Ubuntu Tweak ticked).

4. Click refresh and type your password in again.

5. Go to Add/Remove and install the software available in these new sources.