Using D3.js to Visualize GIS by Jos Dirksen is a really extensive write-up of his succesful attempt to re-create the Chloropleth example from the D3.js website.

He explains how he converted the shape files into PostGIS, exported them to GeoJSON, and used D3.js to show them. I wonder how this could be integrated with Polymaps.

More info about D3 geo here and here.

Bonus links: