SeatGuru
This is now part of TripAdvisor; this website provides Seat advice with over 700 seat maps, along with over 25,000 flier reviews. When used in conjunction with online check-in or seat selection, you can find the best available seat for your class, and avoid seats that have restrictions or are in unfavourable locations.

SkyTrax
Reviews and over useful information on airlines and airports.

Airwise
A multi-role website that also provides detailed air travel news and information about airlines, airports, aviation and the air travel industry.

 

FlyerTalk
FlyerTalk features discussions and chat boards that cover the most up-to-date traveller information. The forums are open to everyone who travels. This is really useful for such questions as ‘what can I do at airport X while I wait Y hours for my connection?’

Professional Pilots Rumour Network
The PPRuNe Forums (The Professional Pilots Rumour Network). Ever behaved badly on a flight? Then you may get a mention here. It is a community of professional pilots and people who work in aviation, both experienced and inexperienced.

World Airport Codes
World Airport Codes is the place to find airport codes, abbreviations, runway lengths and other airport information for nearly every airport world-wide. Ensure that you fly to the right airport.