is something that requires some hacks in Ubuntu 8.10, and most of the information out there seems to be for earlier versions and will not help in getting gsynaptics up and running on Intrepid. This does work, tested by yours truly.
Start “Add/Remove applications and search after Touchpad. Install it.
Then fire up a command prompt and write:
gksudo gedit /etc/hal/fdi/policy/shmconfig.fdi
and enter the following:
Save, reboot and try out touchpad under System – Preferences – Touchpad
More stuff and conf stolen from here. You really should read that page since it contains a lot more information regarding security and other possible configurations.