http://www.landings.com
The largest aviation server on the Web.  It has thousands of links to aviation sites.  The Search part has searchable databases for N-numbers, certificated pilots, medical examiners, registrations of some other countries, the FARs, Service Difficulty Reports, NTSB accident briefs, world-wide airports, and more.  If you are looking for anything about aviation, here is a good place to start.

http://www.berlin-airlift.de
This server is from the Berlin Airlift Historical Foundation, A Mission of History and Education.  Sites are in english and german language. Aircraft C-54 "Spirit of Freedom" and other aircrafts.
Also see Museums

http://nasdac.faa.gov/internet
This link provides access to several of the principal aviation safety data and information sources the Federal Government uses for various purposes, including the NTSB, FAA Incident statistics, and others.

http://www.omina.com
A club that allows you to travel in a DC-3.  You can either use their travel arrangements or create your own itinerary.  They provide aircraft and crew for travel anywhere in the world. Travel with other groups or gather your own group

http://heritage.stsci.edu/
A growing collection of interesting pictures and associated information from the Hubble Space Telescope.

http://gps.faa.gov/
The Global Positioning System Product Team (GPS PT) web site is designed to inform the aviation community and the public on the FAA's satellite navigation programs and the efforts of the GPS PT related to the development and implementation of these technologies.