In 10.10 that I was using before 12.04, you could use Alt+F9 to minimize a window to the task bar.
In 12.04 Meta+Ctrl+↑/↓ maximizes and unmaximizes a window.
If you have a numeric keypad you can use Ctrl+Alt+0 to minimize to launcher.
On my netbook I don't have a numeric keypad and the normal numbers do not work with the above shortcut. How can I minimize windows with a keyboard shortcut?