Personally, I prefer "Universe of Bagpipes" (http://www.hotpipes.com/), because A) it covers Continental and North African pipes thoroughly, not just Celtic pipes, and b) it has a nice tie-in page on the historical connection between the bagpipe and the hurdy-gurdy (an instrument that has long facinated me). However, it does focus overly on the instruments themselves and gives short shrift to the music itself.