I've always thought that Ubuntu's default look is slightly boring. Not that it looks bad, but there's lots of room for improvement. Here are a few links to help you make Ubuntu look extra special.

Themes:

http://webupd8.blogspot.com/2009/05/9-great-gnome-themes-with-ubuntu.html: here are some of the best Gnome themes I've seen around. Great thing about these is that you can get them from the Ubuntu repositories.

http://www.clububuntu.com/2009/04/10-awesome-themes-for-ubuntu.html

http://www.techiesouls.com/2008/11/27/collection-of-50-best-looking-linux-gnomeubuntu-themes-to-download/

http://www.junauza.com/2009/04/15-beautiful-ubuntu-gdm-themes.html: here are some great themes for your login screen.

Icons:

http://www.junauza.com/2009/05/10-awesome-icon-sets-for-ubuntugnome.html

Conky:

Conky is a superb way to display a whole lot of information about your system on your desktop. For example, you could have visual access to information like CPU usage, memory usage, storage usage, network traffic, and lots more.

http://www.linuxhaxor.net/2009/05/07/8-beautiful-conky-desktop-monitor-setup/

http://linuxowns.wordpress.com/2008/04/04/create-a-custum-conky-setup/

Gnome:

For lots of visual and other improvements to Gnome, I recommend: gnome-look.org

That's it for now. I've got some more useful links for odds and ends on Ubuntu, which will come in my next posts.