Hiya,
We rolled out this tract-level map of broadband adoption for the most recent data available.
The definition of broadband that the FCC actually releases the data at is amazingly antiquated (768Kbps/download; 200Kbps/upload) --but it's the best public data set we've got for tracts. We also ran a Monte Carlo simulation to get city-level adoption rates too: http://investigativereportingworkshop.org/investigations/broadband-adoption/htmlmulti/broadband-subscribership-100-largest-us-metro-area/
Broadband adoption map 12/08-12/10, by tract
investigativereportingworkshop.org