As users become more experienced with Linux, the almost invariably learn to love (or at least tolerate) the powerful command line interface of the terminal. For super-quick access to the terminal window, I recommend a handy utility called Tilda, which places the terminal in a dropdown menu at the top of the screen. Hit a key and it slides out from just beneath the panel. Hit a key again and it slides back up again.
To install Tilda, just search for it in the Synaptic Package Manager. Once installed you'll need to make it autostart on each boot by adding an entry within System, Preferences, Startup Programs (click the Add button and type tilda into both the Name and Command fields). Tilda's preferences let you set a hotkey combination to hide/unhide the prompt, and I use Ctrl+Space (right-click Tilda's window and click Preferences to change the settings).
The beauty of Tilda is that it's always there in the background. I can start a system update with sudo apt-get upgrade, for example, and then hide the Tilda console until it's completed. There's no risk of accidentally closing a terminal window and thereby killing any processes I started.
It also means I don't have several unused terminal windows hanging around on the desktop. Just like a standard terminal window, Ctrl+Shift+T will open new tabs in Tilda (type exit within each tab to close it).
I've tweaked Tilda's settings so the window is semi-translucent, and centred in the middle of the window. See this screenshot for an example of my settings.
Keir Thomas is the author of several books on Ubuntu, including the free-of-charge Ubuntu Pocket Guide and Reference.