I use Skype &
Vassal to roleplay with people in the US, UK, NZ, Czech republic etc. The game we play uses cards like TORG, but custom designed for the game (a pulpy Call of Cthulhu called Heroic Cthulhu). Before Vassal we used OpenRPG, which is an open source free application that has dice rolling & allowed the uploading of maps & pics etc. There are other commercial ones out there, but I cannot comment on how good they are.
With Skype we tend to find 5 people is the limit before it gets too hard due to not having visual queues as to when people are going to speak. I have heard of people using Teamspeak etc as well. You could also try out Voon Voice chat.