Where can I get the FAA data that defines airspace, including MOAs etc.? I was looking at http://www.gelib.com/aeronautical-charts-united-states.htm, where you can download shape files for Google Earth that show US airspaces.  I'm writing some software that has a similar need and need to find a source for this data.  I'm looking for data that defines the extents of airspaces including MOAs, restricted areas, etc.  

I have been pouring through the FAA's website with no luck.  The link I referenced above says its source was the National Aeronautical Charting Office (NACO), which I'm having very little luck finding as well.  I think it may have been renamed, thus the poor results.  I also called the FAA and can't seem to find anyone there that knows where to transfer me.

So, does anyone here have any helpful pointers on finding said information?  I want to pull it directly from the source to make sure it is always up-to-date and accurate.
Take a look at the National Flight Data Center.  The data appears to be contained in NASR. I mentioned in my comment that there may be no official source for spatial data, but I think this may include what you are looking for.
These are derived products. The cannonical definitions are the legal descriptions found in FAA Orders with the prefix 7400. At the time of this writing, JO 7400.11 (current version E) covered airspace classes A,B,C,D and E as well as reporting points. The JO 7400.10 (current version C) covered special use airspaces. Both publications can be found at the FAA's Website.