This is a d3.js visualization of US zip codes.
Original zip code dataset from Geocommons.
5MB shapefile with properties such as zipcode, state, name, population, area, more.
http://geocommons.com/overlays/54893 (Thank you Bill Greer)
This converts it nicely:
topojson \
-p name=PO_NAME \
-p zip=ZIP \
-p state=STATE \
-o zips_us_topo.json \
zip_codes_for_the_usa.shp
I was actually looking for the same thing as @roesler-stan..is there a way to easily parse this file into separate topo.json files by state?