Quick update on the Validator. Code is getting cleaner and is pretty much in a runnable state now. I have a copy running on <URL:http://www.tss.no/~link/ val/> and a snapshot at <URL:http://www.ts s.no/~link/dist/val.tar.gz>. I still have charset mismatch problems to deal with as well as fleshing out ";imgonly" and XML-output support, but it should be pretty much all downhill from here.
Sean Palmer raised the question of XHTML Families and XML Schemas and I've offered to take a look at the problem. If it turns out to be easy (I doubt it) I'll probably include it in this round of sweeping changes (Gerald will kill me! ;D). Otherwise I'll try to work on that next.
I feel a rant about reinventing square wheels coming on every time someone mentions XHTML and the problems with DTDs to me, but I'm trying to keep my mouth shut as I don't really know enough about the subject to venture an opinion. Don't worry though, I'm saving up on vitriol until such time as I feel I'm on firm ground... :-)