Is there a utility that allows to open a terminal window with a shortcut?
Check out iTerm2 (see also the Google project page). You can bind a key combination as a way to show/hide the terminal. In a way, you achieve the same thing as the before mentioned Visor; yet, iTerm2 offers more functionality than Terminal.app. 

Combine this with alfred/quicksilver and iTerm2 profiles for more hotkey awesomeness.