By default an eGalax touchscreen works fine with a Ubuntu. Fine but not perfectly... because drag is not detected.

After a couple of minute searching on the Internet, I found it is a bug and a known bug (link).

so here is the procedure to fix it on ubuntu Karmic

First of all check your device :

[doume]>cat /proc/bus/input/devices

I: Bus=0003 Vendor=0eef Product=0001 Version=0100
N: Name="eGalax Inc. USB TouchController"
P: Phys=usb-0000:00:1d.0-1/input0
S: Sysfs=/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1:1.0/input/input5
U: Uniq=
H: Handlers=mouse2 event5 
B: EV=b
B: KEY=400 0 0 0 0 0 0 0 0 0 0
B: ABS=3

Then patch evtouch and rebuild it :

cd /tmp
sudo apt-get build-dep xserver-xorg-input-evtouch
apt-get source xserver-xorg-input-evtouch
cd xf86-input-evtouch-0.8.7/
rm debian/patches/02-buttonless-device.patch
wget -O debian/patches/02-buttonless-device.patch http://launchpadlibrarian.net/26529094/02-buttonless-device.patch
echo 02-buttonless-device.patch >> debian/patches/series
dpkg-buildpackage
sudo dpkg -i ../xserver-xorg-input-evtouch_0.8.8-0ubuntu3_i386.deb

This procedure works perfectly for me and make Enna sexier ;)