I've tried lots of distros (SuSE, Slack, Fedora, Mdk, etc...), but not Debian (Yet.). I understand it's a bit different, but I'm hoping this info will help (it works under Mdk 10.1, Slack 10, and SuSE 9.2)
This is one of many sites that hosts the synaptics touchpad driver: http://web.telia.com/~u89404340/touchpad/
Download, install (./configure, make, make install, etc). You'll then have to edit your xorg.conf file (usually /etc/X11/xorg.conf)
Find the entry for your touchpad, and set the driver value to "synaptics". Add a new option,
Option "SHMConfig" "on"
Then from the console, run
This will turn off your touchpad while you're typing, for 2 seconds after your last keystroke. You can change this interval (check the README / man files)
Hope that helps!