RPTools is a set of open source tools for playing tabletop games online. The main tool of which is called 'MapTool'. It is a system that was built initially to solve playing RPGs like Dungeons and Dragons online with folks who may not be able to meet in the physical world regularly.
It acts as both an editing environment where you can setup your maps / campaigns / etc, as well as the playing environment where you can actually play the games with each other. One person acts as a DM, and other players connect to the game and move tokens around, roll dice, set states, etc. all as if you were sitting around the table.
I cannot say enough how amazing of a tool this is, as it has saved our D&D sessions when friends have had to move out of state, as well as how it has made the gameplay itself much easier than it ever was with pen and paper.
The tool itself is flexible enough to support any RPG you can think of, and It would probably even be able to support any board game you could think of.
I highly encourage folks to check it out:
Check out many of the video tutorials to learn more:RPTools TutorialsYou Tube
Also download the tools yourself at their home:RPTools Home