100LL.com - 100LL.com is a pilot's information service with a continuously updated nationwide airport directory with aviation fuel prices including 100 Low Lead and Jet-A, hotels, ground transportation, airport services, and more.
AirNav - AirNav provides free detailed aeronautical information on airports and other information to assist pilots in gathering information for flight planning.
AOPA Online - Aircraft Owners and Pilots Association Online
Federal Aviation Administration - The FAA is primarily responsible for the advancement, safety, and regulation of civil aviation, as well as overseeing the development of the air traffic.