If you mean the maps-type interface, just look at the page source - it's a couple lines of javascript. This is just Leaflet's standard behavior. The map itself is a series of image tiles with a predictable naming convention.

Leaflet is great: http://leaflet.cloudmade.com/

Here is the code and some information about handling the traffic https://github.com/dividuum/xkcd-1110

Will i be wrong to hope for a blog post explaining the process shortly?