I’m quite impressed with xplanet (http://xplanet.sf.net/). You can give it a text file containing lat, long, and markers and generate a map of the world with people’s locations on it. Put it on a Wiki so people can edit it and you get
The tricky thing is figuring out how to do just part of the world, such as North America. The world map is a projection but you can’t zoom in on a projected view. Turns out you can put it in globe mode, centre on the area you want to record, and zoom in so that it looks flat.