For those that havent seen them yet, theres a couple of extra repositories you can add to Ubuntus software sources list. This lets you get alternative files from synaptic / apt-get. The main ones i have enabled are Medibuntu and Playdeb. There are others out there though.
Extra repositories can be added by opening the System menu on your desktop, selecting Administration, then Software Sources. Click on the Third Party tab. Click add and enter the repositorie address in the space provided.
For example, to add Skypes repositorie copy and paste this line into the address line: deb http://download.skype.com/linux/repos/debian/ stable non-free. It will ask you to reload your sources list when you close the software sources box. Heres a couple of repositories you might be intrested in.
Medibuntu
An Ubuntu repo including Google Earth and Skype. Theres a list on the wiki, linked to above.
Playdeb
A games repositorie, its currently in Beta, but works fine for me at the moment. I advise against using this untill its officialy released unless you are happy using something that may cause problems on your PC.
Ubuntu Tweak
The link above tells you how to add Ubuntu Tweak to your source list.
E17
This page is for adding the Enlightentment desktop to your Ubuntu repositories.
Theres a nice guide to adding extra Repos on ubuntus website HERE
with images to make it easier ^^ .
To find more repos, click the repositories catagory to the right of this post.
I hope someone finds one of these usefull. Take care!