There's a lot you can do once you bring your spatial data into the web browser, but how do you get it there? Josh Livni and Paul Saxman show you how to quickly bring in data from the venerable shapefile to cutting edge TopoJSON, and then go over some best practices for client side cartography.
Links:
/ (Shp Escape)
(City Pop Viz)
/ (Mike Bostock's "Let's Make a Map" post)
/ (Natural Earth)