ZM Quad Chess is a 4 player chess variant that I personally love. It's not well known since the president of the chess club where I grew up and one of his friends developed the variant over several years. However, if you google for it you'll find the rules for it easily. The ZM stands for Zimmerman and Moon (the last names of the two guys).
It's been a long time since I've played it, but I always have fun with it.
As anyone here ever paticpatied to such madness? If so, please share your experiances.