This site has heaps of info about the history of dragons in various cultures, and even something about the physiology and anatomy of dragons.
I've yet to check it for accuracy e.g. whether the Maori word for dragon really is 'tarakona' (I thought maybe it was 'taniwha'?), and there is a bit of a commercial side to it (you can buy dragon merchandise on the site). But the author seems to simply be genuinely interested in dragon mythology.
I'd like to know her source for the anatomical drawings.