webdiplomacy.net

How about a blind variant in which each player knows where his or her units are, but, they can't see anyone else's units, just who owns each place on the map.

This could make for some incredible backstabs, like a completely invisible convoy from North africa to brest or gascony.
Although, I do feel like this obviously overpowers countries with fleets as they are stealthy and invisible.

fog of war on vdip

Fog of War on vdiplomacy.com is my favourite way of playing Diplomacy, especially Gunboat. They have implemented it very nicely there.

Captainmeme ran a blind dip game a few years ago on the site. If memory serves, Austria soloed. It was beyond FoW because you never saw enemy units. Isn't FoW where you can see enemy units that are adjacent to territories you occupy?