This is a great site! I like http://mbostock.github.io/d3/talk/20111018/force-states.html and especially http://mbostock.github.io/d3/talk/20111018/azimuthal.html which is really good for demonstrating the differences in projections.
Thank you for sharing this!
Colleen R. Cahill
Digital Conversion Coordinator
Geography & Map Division
In their (impressive!) Gallery https://github.com/d3/d3/wiki/Gallery I found this one that may be of interest to this community:
Chief, R&D, Congressional Research Service Group
Library of Congress