This one lists as many of the known airfields in all 50 states as possible:

http://www.airfields-freeman.com/index.htm

This one lists information on all known airplane crashes in the 50 states. Pretty darned sobering stuff.

https://planecrashmap.com/

That pretty cool. It shows some of the really small auxiliary fields around my home town that were used then the Air Force was training pilots in the 60s and 70s. Suprisingly has some really good info and pictures. I have some info on them I plan to submit.