My variant is this:
The normal board and pieces are used. All the normal rules apply, with the following exception: on any turn, the player may move more than one piece (once each), in any order, as long as he does not make a capture, initiate check, or respond to check. Otherwise, he may only move one piece, as usual.
The overall feeling of the game is that of a battle, with very quick, coordinated, dynamics. You may call it "Leandro's Chess", after my Internet Chess Club handle! The idea is that a player must balance movement with combat. As in a battle, a player may move more than one piece, with the pieces moving together in a coordinated way. But combat resolves itself one move at a time, as in standard chess, to accommodate the resolution of combat to a turn system and avoid a dynamic imbalance created by the advantage of who's turn it is.
The game tends to resolve itself fairly quickly, but is intriguing. Player need to make a choice, turn by turn, whether they will move their armies, or resolve the tension of combat through captures or attacks on the King. This is true of standard chess, also, but this characteristic is highlighted in my variant. I notice, also, that the character of the pieces remains the same as in standard chess, but is highlighted.
For example, the rooks tend to be used as support pieces, guarding the files, until the end game, when they attack. The possibilities are so large on any given turn that it is very hard to calculate them, unlike in standard chess. This leads to strategies based more on pattern and balance. I don't know, but this tendency may make it hard for a computer to dominate this variant--as it can standard chess! On the other hand, this variant seems simpler than standard chess, precisely because calculated combinations are less feasible and one relies on overall strategies.
As far as I know, this is an original variant, although similar to Quest-Chess. I thought of it before finding your web site and learning about Quest-Chess.
I have also implemented Leandro's Chess for Zillions of Games. You may download the ZRF and images zip file here. The ZRF also includes a couple of sub-variants that I find interesting. I would like to "warn" any ZoG users, however, that this ZRF is very large and much too cumbersome for the ZoG artificial intelligence engine. I find it useful for playing by e-mail (select both sides), although you still need to be patient because it takes a couple of minutes to load! But if you try to play against the computer, ZoG may hang or crash! You may download a ZoG saved file of an e-mail game I played here. Enjoy.
Thanks to Peter Aronson for play testing.
I would be interested in any comments.