I know, I know: it's a *baseball* group and not a *football* group, but Trey Caussey just posted the last few years' worth of NFL play-by-play data in (unsanitized) SQL format. I'm sure there is some crossover in this community, so here is a Dropbox link to a big ol' ZIP file with everything in it.
Haven't looked at it myself yet. Let me know what you think.
-Bryan