Alan Ng's site isn't really very useful unless you're looking for references to modern recordings of tunes with little useful associated information, but no doubt it serves some purpose beside feeding his ego. The Fiddler's Companion is far more informative and less pompous, but as "Guest" mentions, much of the data are taken from unreliable sources which need to be checked independently. There's a lot of stuff there that's quoted from Grattan Flood and Robin Williamson, for example; the former is long discredited and the latter, however much affection we might have for the Incredible String Band, is far from being an expert.