After I've set up network connectivity, one of the things I invariably configure on a newly installed Ubuntu system is Synaptic. Synaptic has improved drastically since the first releases of Ubuntu so that things are much easier now.
So what's to set up in Synaptic? The repositories, mainly. Out of the box, Ubuntu gives you the officially supported applications, highlighted by the Ubuntu tri-color cycle logo. It's good enough if you want the basic applications.
But if you need a bit more, you'll want to look into additional repositories. Here's how to set them up.
First, fire up Synaptic. It's accessible from
System->Synapticof the main Ubuntu toolbar. (On Xubuntu, it's
Applications->System->Synaptic Package Manager
On the Synaptic menu, click on
Settings->Repositories. This will bring up the Repositories dialog.
Activate the selections for the Universe and Multiverse checkboxes. Click on
Synaptic will remind you to reload the repositories as the repository info has changed.
Reloadbutton on the Synaptic toolbar. Synaptic will then begin loading the information on additional software packages. This should take a couple of minutes.
When you're done, you'll have the full library of Ubuntu applications available to you.