People often hear the pipe organ more in December than in other months, thanks to the profusion of Christmas-centered church services and concerts. Here to give us a "crash course" on this mighty instrument--its anatomy and its history in various geographical regions--is noted U.S. organ consultant, restorer, and builder John Bishop, owner of John Bishop Organ Consultation. He is also the Executive Director of the Organ Clearing House, whose mission is to "rehome" unused or unwanted organs. Additionally, John writes a monthly column for the organ journal The Diapason 

Other organ resources, including videos of historic organs that John selected for us: 

Gwendolyn Toth plays Scheidemann on the 1457 organ at Rysum   Visit to the oldest organ in Holland, Oosthuizen, 1521   Considered the oldest organ in the world, Sion Switzerland, 1390. This one is especially charming because Guy Bovet playing the music of Haydn (1730-1809). The organ is nearly 400 years older than the music.

Vox Humana, a web magazine of current organ research/trends