After installing Ubuntu 10.10 on my 
Asus eee T91
 I was pleased to notice the touchscreen was working out of the box.  Unfortunately the calibration was off and I could not find the calibration utility. 
These instructions are now deprecated and I recommend using the xinput_calibrator utility which can be found here:
http://www.freedesktop.org/wiki/Software/xinput_calibrator
This old method is left here for reference only.
I was able to successfully calibrate my screen using the following method:
Open a terminal and type the following:
xinput list
You should see something like this:
⎡ Virtual core pointer                     id=2 [master pointer  (3)]
⎜   ↳ Virtual core XTEST pointer               id=4 [slave  pointer  (2)]
⎜   ↳ IDEACOM  IDC 6680                        id=8 [slave  pointer  (2)]
⎜   ↳ IDEACOM  IDC 6680                        id=9 [slave  pointer  (2)]
⎜   ↳ SynPS/2 Synaptics TouchPad               id=13 [slave  pointer  (2)]
⎣ Virtual core keyboard                    id=3 [master keyboard (2)]
    ↳ Virtual core XTEST keyboard              id=5 [slave  keyboard (3)]
    ↳ Power Button                             id=6 [slave  keyboard (3)]
    ↳ Sleep Button                             id=7 [slave  keyboard (3)]
    ↳ USB 2.0 Camera                           id=10 [slave  keyboard (3)]
    ↳ Asus EeePC extra buttons                 id=11 [slave  keyboard (3)]
    ↳ AT Translated Set 2 keyboard             id=12 [slave  keyboard (3)]
Note where it has the first "IDEACOM  IDC 6680", that's your touchscreen.  There should be an id in the second column ie. "id=8"
pass the id into the next command(I'm using 8 as the example)
xinput set-int-prop 8 "Evdev Axis Calibration" 32 300 7900 400 7800
That should have set your screen calibration, the last 4 values are the actual calibration numbers.  You may need to tweak these numbers for your monitor, so just fiddle with the values and rerun the command  until you are happy with the calibration.
At the moment you will lose your calibration when you reboot so to make it permanent do the following:
sudo gedit /etc/X11/Xsession.d/98x11-common_touchscreen
Paste you calibration command from the step above into the file and save.
 
This will run the command on bootup so your calibration is now set.  If anyone finds a better way to do this please post a comment.
 
These instructions were adapted from posts on this thread on the Ubuntu forums: