OpenStreetMap
I noticed that many of the smaller airports in eastern Massachusetts (and probably elsewhere - I didn't check) are missing. Equipped with the Yahoo! imagery and a recent A/FD (Airport/Facility Directory), I started adding some of the ones I frequent most: Marshfield and Plymouth. This project is to be continued...
Discussion
Comment from Circeus on 31 March 2009 at 05:14
Actually, most stuff that is not TIGER (and even TIGER leaves much to be desired on many accounts!) will be missing regardless, and airports are just an example. The larger ones are likely to have been added by users, but the smaller ones, not so (I added three in Orange County, NY not so long ago).