Touchpad in Ubuntu

Ubuntu installations come with a mouse setup software, but it is a generic software that only allows you to setup stuff like double-click timeout, pointers, speed, etc. If you have a touchpad and want to setup other parameters like tapping speed, you'll have to install GSynaptics:

sudo apt-get install gsynaptics

After installing the software you can find it in the System/Preferences/Touchpad menu. Try to click it and you'll get an error message!

GSynaptics couldn't initialize.
You have to set 'SHMConfig' 'true' in xorg.conf or XF86Config to use GSynaptics

To fix this you need to edit your /etc/X11/xorg.conf file (e.g. sudo gedit /etc/X11/xorg.conf) and find a section like:

Section "InputDevice"
    Identifier     "Synaptics Touchpad"
    Driver         "synaptics"
    Option         "SendCoreEvents" "true"
    Option         "Device" "/dev/psaux"
    Option         "Protocol" "auto-dev"
    Option         "HorizScrollDelta" "0"
EndSection

Before the EndSection add an option with the code Option "SHMConfig" "on".

Now you need to restart X. Make sure you save all your work, because restarting X will log you out. Now press ctrl-alt-backspace. Login and you should now be able to run System/Preferences/Touchpad.

If you still have problems using your touchpad, refer to this complete guide.