The Aeronautical Information Manual (AIM) is a federal publication that contains guildlines and procedures for aviation in the United States. While not a regulatory publication, it is extremely useful in bringing about a standard of aviation related operations. It contains information such as airport markings, procedures for communicating with air traffic control, instrument approaches, aviation meteorology and much more information regarding safety of flight.
It is an excellent soure of information and required reading by good flight instructors. It is also good to review it once in a while.
All of the documentation in the AIM can be found at http://www2.faa.gov/ATPubs/AIM/.