The History of Phone Phreaking. A very cool site about the history (and history it is, going waaay back) of phone phreaking. With interesting information about the process of researching that history.
Found via Jason Scott: The FBI File of Yipl/TAPInteresting thing to try: see if I can get CÆSAR, an open-source MF / DTMF generator or blue box for Linux working to make a call to the Project MF server to simulate blue boxing. But it will be from a phone behind an asterisk test server so I don't have to pay to call a US number.