Four Way Chess

If you had a Java-capable browser, you could play Four Way Chess (Taurus Two-Team Chess) here.
Keys "s"=save "l"=load "b"=back once

Taurus Gaming produces a handsome-looking, reasonably-priced playing mat, and a recommended rule change: If you are checkmated on your turn, your army disappears and the opponents then alternate with your partner move for move. In this version of four-way chess, you may not capture a unit belonging to your partner.

Chess Variants

These are simple illustrations rather than strong opponents.