Aviation Search Engines: N-Numbers--Look up aircraft registration numbers for owner, type, and other information.

Greg's Common Commercial Aircraft Spotter's Guide--a very informative guide to identifying commercial jet aircraft.

The Aviation Enthusiasts and Spotters Webring--an listing of excellent spotters' sites in Europe and Asia.

Aileron's Guide to Plane Watching--Plane watching information for airports in North America.

Aeromoe's U.S. Airline Fleets--a must-see listing of all commercial aircraft fleets with individual aircraft histories. (absolutely required for plane spotting, although portions are out of date)

Plane Spotting Reviews of Major West Coast Airports and Beyond--In-depth reviews and descriptions by Paul Shindelus about plane watching at 10 (and growing) major airports on the West Coast.

Plane Spotting Home Page--a digest of information on plane spotting at airports world wide (by region).

The Spotter's Home Page--Marco Dirkx's wonderful resource for spotting military aircraft.

Brian's Planespotting Site--excellent resource for spotting at airports on the East Coast, especially in Florida.
 

For Photos of and Information About Airliners and Airports

Airliners .Net - Commercial Jet Airliner and Aviation Photos--Outstanding database of aircraft photos!

Vince's Old Airliners & Transports--photos and information on vintage commercial aircraft.

What Do Navaids Look Like?--A great examination of what all sorts of aviation navigational aids look like and how they work by Dale Dickerhoof.

The PSA History Page--Kevin Trinkle's great web site in tribute to a great Southern Californian Airline.

Mailing Lists of Interest to Spotters--A compilation of several emailing lists covering spotting, airlines, and military aircraft.

The Commercial Aviation Enthusiast Home Page--A new site with photos and links to airports, airlines, and other aviation pages.