PBP data through week 4 is now available here. As in previous years, I plan on updating it throughout the season, around each quarter-mark. Previous seasons can be found here. The first download of the year is always the most troublesome, so future updates should be quicker.
That is very cool, but wouldn't one also need a large set of data from previous seasons to train new models? How would somebody get their hands on that?
You haven't been reading this blog very long have you, X? http://www.advancednflstats.com/2010/04/play-by-play-data.html
Didn't mean to be snarky, sorry about that, but Brian's provided years of NFL PbP data in the past.