Federal Aviation Regulations: A form based interface to search most of the FARs. Use it to specify searches using different words in different parts of the FARs.
Regulations: On-line access to most of the FAR's. They are in HTML format with one file per paragraph. They contain hyperlinks between paragraphs and sections, making cross-references possible.
Advisory Circulars (AC's): FAA's main index of AC resources. Includes Regulation & Certification, Airport, ATC, and Commercial Space Advisory Circular links.
Supplementary Type Certificates (STC's): FAA's main resource for the STC program. Includes a information on the registration of a new STC, STC search, faq, and overview of the format of STC's in their database.
Airworthiness Directives (AD's): FAA's emergency AD resource, with links to other areas of the FAA's site dealing with Airworthiness Directives.