I don't have time to write much, sorry...
This works with the kit fidodido is selling on Ebay (that's where I got mine), and allows you to use it with the stock Xandros even if you didn't remember to ask him for the Xandros-ready touchscreen controller.
It's a compiled version of the sources which are available from eGalax. Read their documentation for usage instructions. To get it to work, I renamed the usbtouchscreen.ko module to prevent it from being loaded, created a device node at /dev/tkpanel0 as per the eGalax module building instructions, put my tkusb.ko module in /lib/modules/2.6...-eeepc, ran "sudo depmod -a" because it felt like The Right Thing To Do, edited my xorg.conf to specify the Device for the EETI section as /dev/tkpanel0, and then rebooted.
I tried blacklisting usbtouchscreen in /etc/hotplug/blacklist, but it had no effect. Renaming the ko file is dirty, but it works.
When it's working, you should find that pressing on different bits of the touch panel makes the mouse click on different bits of the screen. That's what touch panels are for! :)
You're likely to need to calibrate it, though - run the Touchkit program, from the eGalax driver distribution, to do that. If it hangs for ages, it probably means you've got the usbtouchscreen module loaded, which comes with Xandros. Rename it to stop it loading in future, and reboot to kill it. It lives in /lib/modules/2.6.21.4-eeepc/kernel/drivers/usb/input.
After doing that, everything works fine for me - now I just need to open up the EeePC again and fit the screen internally.