Censuous - a beautifully designed, non-technical web interface to pull census info into kml or shapefiles.
Getting data out of the census is non-trivial, even when you know your SF1, block groups, GEOIDs, H04001, etc. The barrier to easy data access is still slightly too high - the place-based summaries are great, but mapped data requires just a bit too much knowledge to be really accessible.
This one is such a no brainer. No need to describe it further.
