To kill some time many years back we wrote a 32-player "chess" game. We had some slightly modified rules, most notably anyone can move themselves whenever they want to and "killing" the king was a matter of checking him for a specified amount of time (say, 10-15 seconds). It was still black vs white.

The game turned out to be very fast paced, to the point where we had to add measures to slow it down. :)

As I recall, it was written with the "board" as a separate entity from the pieces. The board contained the game-rules, for instance whether it was turn-based or not. Now, this is what got me thinking... The platform we used, allow for live recompiling and upgrading of objects -- so we indeed did go in and change the rules even as a game was running (which was kind of fun, just to mess with peoples heads). But I do think perhaps that could be a nice twist to have as a "service" as well -- the ability for people to design their own chess-rules by giving them a framework (like, standard board, standard knight, pawn etc). Naturally saved online, for public scrutiny. :)

It would be be fun to see what people came up with. The target group for this may be somewhat limited. :-)

A friend has a version of what we made hosted on his personal site, but I'm afraid to link to it because it'll probably bring down his server. Throw me a mail if you want the link.