We use a program called Klooge to run our weekly game.
This virtual table top program allows us to have both players at the table and players from the Internet to be able to interact with each other during our weekly sessions.
Klooge is Java based program so anyone using any operating system can log into our game. The program handles most of the rule functions also so that players can concentrate on the roleplaying aspects of the game rather than game mechanics.
There is a very vibrant community that supports Klooge on the company forums (where I am a moderator) as well as several player generated sites.
BOB's Klooge files has a some of the files we use in our game.