A comprehensive database of Military Aircraft :

Computer Aided Design of Aerospace Concepts (CADAC):

An open source software - Modeling and Simulation of Aerospace Vehicle Dynamics, Second Edition - developed by the US Air Force. ( enter password CADAC4)

The Air Force Research Laboratory:

An Aerospace portal from Cranfield:

Aeronautics and Space Engineering Board:

Canada Aviation and Space Museum:

The Chandrayaan Moon mission:

A vast database of Russian helicopters :

A very comprehensive database of helicopters, by country:

A famous site for commercial aviation and aviation photography

A huge aircraft search portal with over 10,000 aircraft listings from over 1800 aircraft dealers and private sellers.  Also features aviation services and resources.

Source of cost-free reference material for aviation historians, researchers, writers, and scholars.  More than 10,000 types of U S aircraft, their models, their specifications and data, and informative text.

This site has a number of databases that provide useful information to visitors: NOAA Approach Plate Database, FAA Written Exam Prep, Aircraft Background Investigation, Aircraft Performance & Specifications, Homebuilt / Experimental Database, Translated METAR and Weather Center.

U.S. Air Force, Navy, Marines, Coast Guard air bases, units, organizations, links, tail codes, abbreviations.

Advertiser listings searchable by company name, geographic location and/or product/service category.  More than 27,500 company listings, located in over 185 countries worldwide, over 95,000 products in more than 6,000 categories.

NASA Dryden Flight Research Center Historical Aircraft images :

NASA Aeronautics Research Mission Directorate (ARMD)