Pinwheel Chess is a four-player, all-against-all Chess variant played on a pinwheel- or cross-shaped board of 89 squares, using the pieces typically used in 5 x 5 mini-chess variants. All the regular Chess moves -- castling, Pawn double-move, en-passant capture and Pawn promotion -- are allowed.
Pinwheel Chess: http://www.ship.edu/~cgboeree/pinwheel.html