There is some really fantastic stuff here. I'm especially excited about the maps, American[1] and otherwise, but the stereoscopic views[2] are amazing. They really give you a feel for what it must have been like to view these things. A fun technological trip.
Wow, this is really great. There really is a wealth of knowledge and culture here. I'm especially interested in the collection of sheet music. It would be really great to make an album with new recordings of the old songs.
1: http://digitalcollections.nypl.org/collections/5cd94760-c52a... 2: http://digitalcollections.nypl.org/collections/robert-n-denn...