FidoNet
A worldwide hobbyist network of personal computers which exchanged e-mail, discussion groups, and files. Founded in 1984 and originally consisting only of IBM PCs and compatibles, FidoNet grew to include such diverse machines as Apple IIs, Ataris, Amigas and Unix systems. Though much younger than Usenet, by early 1991 FidoNet had reached a significant fraction of Usenet's size at some 8000 systems.