There are quite a few ways to do this. I could start a project like this to plot CL alumni around the globe.
Great resources: https://productforums.google.com/forum/#!topic/maps/baw9A5LuS3o
An example: http://onlinecustommaps.com/
API might be another way, using Javascript and such.: https://developers.google.com/maps/documentation/javascript/examples/marker-simple