Q:

Is there a utility that allows to open a terminal window with a shortcut?

I often use the Terminal application, especially to commit code to a Git repository, and I don't want to have the window always open. Is there a utility that allows to open a terminal window using a shortcut?

A:

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.

A:

DTerm may be exactly what you are after: it's like a file location aware terminal that pops in and out of view. So you can activate it while you've got a file selected in terminal (or XCode, or whatever) and take an action on the file (like commit a change) and then it gets out your way.
It's free and also available on the Mac App Store.

A:

Visor does that: http://visor.binaryage.com/
In case you just want a command line, use: http://decimus.net/DTerm/

