Kartograph is looking promising. It’s a new Javascript map library that is fully vector based, drawing maps in SVG. First time I’ve seen a complete break with the slippy map raster tiles that Google made so popular. The nice thing about a vector map is you can easily use your own projection. Of course you can do raster tiles in many projections too, but most of the existing raster libraries have Google Mercator baked pretty deeply into them. Also vector rendering is beautiful and somewhat scale invariant.

The code’s on GitHub. And if you dig into the demo pages you can find the source code hidden inside the <div> element that contains the map itself. It looks pretty straightforward, a nice API. I’m a bit alarmed to see methods like “chloropleth” and “dotgrid” right on the map object; that suggests the author has in mind a set of hardcoded visualization types. I hope he’s left room for other developers to easily add their own visualization types. Also none of the examples have any navigation, none of the usual pan/zoom controls we expect. That’s totally fine for many visualizations, but may distinguish the uses of this library compared to Leaflet and friends.