Gnome Guake is a sniffy little tool that help you access your command line. Once you launch the launch the Guake, it is tucked nicely in your bottom-right hand tray. Just press F12 and you have the command line. You can have tab functions for several command line screen similar to Mozilla.
To install just
# apt-get install guake
For more information on Guake, you can look at Guake Website