Does anyone know of an HID-compliant touch screen that will work straight out of the box with Max OS X 10.6 without requiring any drivers to be installed?
Google found a couple of possibilities; I haven't tried them myself:
There's the Wacom Cintiq; while I believe they need drivers I'm sure they'd be available close to day & date.
And an entirely different approach to take might be the Axiotron Modbook.
Would you be happy with an HID-compliant touchscreen running another OS (or OS X with drivers installed), and then a full-screen VNC to your driver-less OS X machine? You might not be able to tell the difference.