Here are some ideas for futures trips I've heard suggested. Add your own!
La Posada, Winslow, and the rail yards.
B-17 crash site on Humphrey's (http://www.aircraftarchaeology.com/b17sanfranpeaks.html) This will require a strenuous hike.
Tunnels under Flagstaff. This one will take some networking.
Tunnels under campus. Likewise.
Luke Air Force Base (best in winter).