Ornitaxa (Rolf deBy)http://www.ornitaxa.com/SM/TaxChanges.html
Dutch webpage on avian taxonomy, containing the Sibley and Monroe list and an extremely useful list of additons and splits since 1993.
World Bird Info (John Penhallurick)http://worldbirdinfo.net/
General comprehensive database of all birds of the world.
A huge database, hoasted by BirdLife International, on bird names and distributions.
The Copenhagen databaseshttp://www.zmuc.dk/commonweb/research/biodata.htm
Description of the databases found at the Zoological Museum of Copenhagen, which form the basis of much of the current macroecological research.