I've been looking into Linux touchscreen drivers for a while now for my carPC, so have a look at the forums here (lot of information on this site) http://www.mp3car.com/vbulletin/
And also at this one which is a forum for a specific carPC distro called LinuxICE http://forums.openice.org/viewforum.php?f=20
. It's a quiet forum, but kev000 is a very helpful bloke.
As far as I remember from my research, I think there are only 2 or 3 main "types" of touchscreen, so there are only a few generic drivers about, which should work for most types. Please don't quote me on this though - I haven't bought my touchscreen yet so have no idea if this is actually the case!