Check out this version of chess . I've heard of this, but had not really seen it before. Click on the link here to see this blog post on it.
I searched 3-way chess at wikipedia and found a link to Three-handed Chess.
From the above wikipedia page, I found more information on Three Player Chess. It looks like sometime in the mid 1990's this chess variant was invented.
I can hardly manged the normal chess board and complexities. But adding a third player to the mix makes for a very interesting and complex game. As one of the posts pointed out, if two of the players don't like the 3rd, then the 3rd player is doomed.