Dieter wrote:
[ ... ]
> You could add DragonflyBSD.  Maybe Solaris, they are supposedly
> becoming some form of open source.  Maybe Apple's OS X, although
> I wonder if there are or will be any open source OS X drivers.

Sure.  http://www.opensource.apple.com/darwinsource/10.3.7/

...most of the things with capital letters (IOKit) are drivers.  Apple's site 
wants you to login first, but they are available via CVSweb on opendarwin.org:

http://cvs.opendarwin.org/index.cgi/src/IOKitUser/

-- 
-Chuck