If you install the default "ubuntu-desktop" you also get with it a gigabyte of crap that you will never use. But if you don't install the ubuntu desktop, you get a system with a text-only login: prompt, and it's not clear what to install to get it to a usable state.
I have an irrational need to optimize my Ubuntu installation. I did some investigating and came up with this method, which gives a minimal graphical 1.2 GB install, with gnome, networking, and no applications.
When you get to the "task selection" screen with the option to install ubuntu base server, kubuntu, etc, do not change anything at all.
sudo apt-get install gnome-panel gdm gnome-terminal
This will install a graphical environment and the login screen, so it will let you login by clicking on your username.
When it completes, reboot using "sudo reboot", or if you are super-geeky, type in the secret command to avoid rebooting.
sudo apt-get install network-manager network-manager-gnome gnome-power-manager hibernateThat will give you a battery monitor and the icon that lets you configure wireless networking. It also gives you the hibernate button when you shut down.
sudo apt-get install chromium-browser flashplugin-installer
sudo apt-get install ubuntu-artwork
sudo apt-get install gnome-panel gdm gnome-terminal network-manager-gnome network-manager gnome-power-manager hibernate chromium-browser ubuntu-artwork flashplugin-installer