I have several interactive maps at The Best Sites For Learning About World Refugee Day that show the flow of refugees around the world.
They tend to be confusing – at least, to me.
The University of Zurich, though, has developed a new one called Refugee Movements which is clean, clear and easy to use. The screenshot at the top of this post shows its interface, and the site has a slider at the bottom that lets you change the years.
Thanks to Google Maps Mania for the tip.