This page : Synaptics Touchpad : Community Ubuntu Documentation has a fantastic fix for the problem of bumping the touchpad while typing. This is a big problem typing on the Compaq CQ60 215DX, the laptop I use. It has a large touchpad and the natural position of my hands while typing causes me to bump it which is very annoying as this treated as a mouse click.

To fix this problem you must first enable SHMConfig (only for Ubuntu 9.04 or earlier, skip this step for 9.10 or later). Create a new file called /etc/hal/fdi/policy/shmconfig.fdi and put the following text in it:

  
    
      True
    
  

Reboot the computer.

Now add the following command to startup (omit '-S' on 9.10 or later):

syndaemon -t -i 1 -S -d

There are a couple ways to do that. If you are using a regular Ubuntu / Gnome desktop you can add it through System -> Preferences -> Startup Applications. If you are using KDE / Kubuntu you can add a startup script to this folder:

~/.kde/Autostart

Such a script would look like this (omit '-S' on 9.10 or later):
Kubuntu 9.04:

#!/bin/sh
syndaemon -t -i 1 -S -d

Kubuntu 9.10:

#!/bin/sh
syndaemon -t -i 1 -d

You could save the file with a name like:

~/.kde/Autostart/syn.sh

The file should be made executable. You can do that with the following command:

chmod +x ~/.kde/Autostart/syn.sh

Now, after the next reboot, or if you run the script manually, the touchpad will ignore bumps that cause clicks and scroll events for one second after every key press. So, as long as you are typing, no disrupting clicks.