use synaptic to install:
ubuntu-restricted-extras
miro
vlc
compiz-icon
and whatever applications you fancy - no kernels or server software; basically just don't get creative!
gnome-do has a docking facility in its settings and there are other docking tools (avant-window-navigator is one)
It all depends on what you want the computer for. Music, graphics, programming, animation, ipod, office tools, DTP, math, electronics, chemistry.
You can play PS2 games with pcsx2, use a wiimote for whatever (games or replace your mouse) have the computer lock when you walk away with a bluetooth device (phone) in your pocket and open when you return, design web pages or google apps and the list goes on. I have some exceptional apps installed not all from synaptic. Boxee is good and songbird. I have several circuit board simulators, all kinds of graphics and animation tools and the best programming tools and educational tools available. I use vboxgtk (or virtualbox-ose) to run different operating systems (all windows, linux, solaris and BSD OS's including windows 7)
Basket for note is awesome - I use instead of a text editor for writing anything I need to write (except for coding when you have to use a text editor or when I use scribus) as you can just drop pictures and links in. I wish these pages would allow that as it would be easier to show people stuff (screenshots etc) (I can't wait for google wave!)
Anyway if you have any questions email and good luck and welcome to linux.