I was chatting with some members of the 80sbbs mailing list, and they came up with some suggestions for how to find telnet-accessible BBS nodes on the modern internet.
These nodes are 1980s-style BBS systems or "boards" which have been connected through a modem emulator to the telnet protocol, so that you can connect from a modern system hooked up through broadband (or dial-up, for those hanging on).
In addition to being fun, these dial-up telnet BBSen are also relatively secure, simple, anonymous and off-radar. The latter makes them an ideal place to use private email to communicate among a group, and for public discussion, since the Facebooks and Reddits of the world have trashed that.
To get onto these boards, all you need is a computer with the telnet protocol installed.
Here are three listings of telnet BBSes that you can connect to: