I recently built a web-based tool for visualizing usage of Tel Aviv's municipal bicycle rental system using D3 and mapbox (warning, hebrew): http://telostats.com
Source is up at https://github.com/idan/telostats, janky though it may be. This was my first effort with geo and D3, and I'm a python person, so the JS is probably eight different kinds of terrible, but hopefully it's useful. There are a lot of examples like the OP's blogpost where D3 is used to render geometry, but very few that show you how to use D3 as an informational layer above an existing slippymap (which is what we did).
Source is up at https://github.com/idan/telostats, janky though it may be. This was my first effort with geo and D3, and I'm a python person, so the JS is probably eight different kinds of terrible, but hopefully it's useful. There are a lot of examples like the OP's blogpost where D3 is used to render geometry, but very few that show you how to use D3 as an informational layer above an existing slippymap (which is what we did).