I got this idea from a post on the BinRev forums. I want to set up an old computer and put an old DOS-based terminal program on it. Then I'll call a BBS with it, assuming I can find a working BBS somewhere in the U.S. I'll do this using the new Google Voice.
I haven't thought this through too much yet, but I think I would need to plug a regular home phone directly into the DOS computer's modem jack. Then I would need to run a wire from the phone's earpiece into my laptop's mic input and a wire from the phone's mouthpiece into my laptop's earphone output. Then I would need to power the phone line with 9 volts once I attempted to connect to the BBS with the DOS computer.
I know high baud rates are unlikely, but maybe I could get it running through Google voice at 1200 or 2400 baud. I don't have my hopes up too much, though, since I can barely even send a fax using MagicJack.