FIDOnet is the largest amateur computer bulletin board network in the world. (I just shut down my BBS, StormGate Aerie, but Net 102 is still there.) For information, see The Fidonet Network in North America , Frank Robbins FidoNet (Resources - Support - History) Site or Collin County Station (My thanks to Frank Vest) See also the weekly newsmagazine FIDOnews.

There are a number of FIDOnet bbss reachable from the internet, notably Doc's Place. See the following webrings for more examples:
FidoNet Official Web Ring
FidoNet World Wide Webring
BBBS Websystems
TriBBS Webring

A copy of the nodelist (and a lot of other stuff) can be found at the IFDC Filegate Project site

The above addresses were obtained through webring.org which I recommend for finding webrings on a wide variety of topics.