I have the tri-D chess set from franklin mint. There is TOS version and a
TNG version. The TOS version has 4 2X2 movable boards where as the TNG
board has 6. I own the TOS one but I do not think franklin mint is
selling them anymore. I managed to find a set of rules made in the 70's
in one of the Star Trek Giant Poster Books. I belive it is volume
14 that has the rules in it. There is also a version of tri-d chess that
you can play against a computer at this site.
http://members.lycos.co.uk/cmparkin/goodies.htm