syndaemon is a program that monitors keyboard activity and disables the touchpad when the keyboard is being used. If you are using Ubuntu / Debian, syndaemon should already be installed and all you have to do is type this in a terminal to start it as a daemon:

syndaemon -d

To set the time you want syndaemon to restore your keyboard, run this command:

syndaemon -i 4 -d

Where "4" is the time between the period you stopped typing and when the touchpad becomes active.