Often time, when working on laptop, my hands touch (tap) the touchpad while typing, which is really annoying, cause I end up writing in different location. Disabling the touchpad permanently is not a good idea, specially if you don't have a mouse with you. Fortunately, there is a very neat tool that monitors keyboard activity and has the ability to disable the touchpad during that event. The tool is syndaemon.
$ syndaemon -d -i 1
That would execute syndaemon as daemon and set 1 second as the delay period.
To automatically run this daemon, for example in KDE desktop environment, I created a script which contains the code above, make it executable, and put it in ~/.kde/Autostart folder.
Also check out synclient, taken from the 'man page', synclient - commandline utility to query and modify Synaptics driver options.