Telehack is a simulation of a stylized arpanet/usenet, circa 1985-1990.
It is a full multi-user simulation, including 25,000 hosts and BBS's
the early net, thousands of files from the era, a collection of
adventure and IF games, a working BASIC interpreter with a library of
programs to run, simulated historical users, and more.
On the web: http://telehack.com/
or open a shell and type
Telehack.com supports an open web telnet interface. You can also telnet
directly to telehack on the standard telnet port 23.