There may well be many more class files out there than are currently
available on CTAN.
For instance, nyj.cls, the class for the New York Journal of
Mathematics, has never been posted to CTAN (but will be, shortly).
I suggest some kind of call for submissions to the contrib/supported
section of CTAN's latex section. I suspect there would be a great
many of them.
It might make sense to include these classes as an official part of
latex, so the commercial distributions will include them as well.
Mark

Mark Steinberger  http://math.albany.edu:8800/~mark
Dept. of Math. & Stat 
SUNY at Albany 
Albany, NY 12222  Editor in Chief, New York Journal of Mathematics
[log in to unmask]  http://nyjm.albany.edu:8000/nyjm.html

