University of California at Berkeley

BBN
Bolt, Beranek & Newman

Cambridge
the university in England (not the city in Massachusetts where
MIT happens to be located!)

CMU
Carnegie-Mellon University

Commodore
Commodore Business Machines

DEC
The Digital Equipment Corporation (now Compaq).

Fairchild
The Fairchild Instruments Palo Alto development group

FidoNet
See the [165]FidoNet entry

IBM
International Business Machines

MIT
Massachusetts Institute of Technology; esp. the legendary MIT
AI Lab culture of roughly 1971 to 1983 and its feeder groups,