TriGo
Keywords: Variant
TriGo is implemented at iggamecenter. Its full rules are described
here.
Essentially, it is go played on a triangular lattice within a hexagon. Each move consists of playing two stones (except for the first move of the game, where only one stone is played).
Strategy
One difference to Go is that, since one is allowed to place two stones in one turn, it is necessary for groups to have three eyes to be alive.