Came across this little gem the other day and thought others on the list 
might be interested.

A FREE X Server for MacOS (and Win95) based on X11R6.  I installed the 
PPC version om my PowerMac, SLIPed into my NetBSD/mac68k system with a 
Null Modem cable and was able to direct my X Windows - in color - back to 
my PowerMac.  This sure beats the price of MacX, White Pine, 
Chameleon/NetManage, Hummingbird/Exceed or any other commercial product 
especially for home use!

The URLs are:
<http://www.microimages.com/www/html/freestuf/mix.htm>
and
<ftp://tnt.microimages.com/pub/outgoing/mix>

-bob