Last week, I was chatting with my friend who lives in France and we were discussing about the driving system in US and France. I was thinking, it was only the countries in North America which follow the "driving on the right" system. It looks like there are around 166 countries which follow the system including France. Others follows the UK System(around 76), that is "driving on the left".
Another interesting thing is that, how the system actually started. It is very well described in the following link.
http://users.pandora.be/worldstandards/driving%20on%20the%20left.htm