http://www.airliners.net (big photo archive of airliners - my favourite spottersite...) here my photos sorted by most popular
http://www.jetphotos.net/ (with information about nearly every western built airliner)
http://www.pilots.de (german airlinerpilots - forum)
http://www.flugzeugforum.de (german aircraftforum, also with english section)
http://www.aviation-community.de/forum-nord/index.php (german messageboard for fans of the northern german Airports: HAM, XFW, LBC, KEL, RLG, SZW...)