I am going to be offerng a game of the Diplomacy variant Treachery in my Diplomacy subzine Eternal Sunshine.  If you're interested in playing, send me an email at diplomacyworld "of" yahoo.com.  If you're unfamiliar with the variant, the rules are below.  It uses the standard game map.

Treachery
By Martin Janta-Polczynski
(rewritten by Doug Kent)

Treachery uses the same rules as normal Diplomacy, with the following changes:

1. With each Spring and Fall season, each player may send one “treacherous order.”  This is an order for a unit of another power. 

2. This treacherous order is followed in lieu of the original order the unit received (as if the commanding general has become a traitor).

3. The Game Master does NOT reveal which orders were Treacherous, nor from which player they came from.

4. In the case that any unit receives two or more different treacherous orders, these orders are not followed and the original “legal” order is used.  If, however, a unit receives multiple treacherous orders but they are identical (i.e. England’s F Nth receives treacherous orders from both Russia and Turkey to move to Yor, and no other treacherous orders) then the treacherous orders are used.  In this example, if a third treacherous order was submitted from France of F Nth-Hel, then no treacherous orders would be used.

Skilled players in this variant will try to take advantage of the treacherous aspect of the game, not just by planning for possible treachery against themselves, but by using the hidden aspect of the treacherous moves to explain away stabs or dot-grabs.  Also, coordinating treacherous orders adds a whole new dimension to the game, as allies can cooperate to effectively commandeer a powers entire armed forces.