FidoNet is strictly regulated, not allowing any commercial content. Candidates have to apply to their region. First locate the major region, like Region 1 for North America. Then, apply to the local region, like Region 13 for Washington, DC. Some web-based gateways to FidoNet exist, and I've noticed some telnet-accessible BBS' offer FidoNet access. There's a FidoNet Newsletter, too!
In my never-ending quest to discover obscure ways to transfer data, I've used BBS', the Internet, private government networks, and amateur radio packet networks. Now I've learned of a system called FidoNet. FidoNet is a system whereby users transder mail and files via modem using a "proprietary protocol." These systems link to gateways connected to the Internet, so mail can be exchanged between the two networks. It seems the appeal of FidoNet is the class of users is different, and there's more of a sense of community.