One of the more exciting and interesting projects in the vintage computing community is FujiNet. Originally developed for Atari 8-Bit computers, it is a peripheral which allows supported devices to connect to the Internet via Wifi and internally handles net protocols which would otherwise require too much overhead for systems of the era.
In addition to networking support, it emulates devices such as disk and cassette drives, serial modems, printers (PDF output), and even allows the mounting of disk images over the Internet to allow booting software/games using a built-in browser. On certain platforms, FujiNet can even emulate CP/M, with the computer connecting to it as a terminal over a virtual serial connection.
One particularly fun use case I’ve found are games hosted on TNFS servers online that have been modified to store their high scores in the network drive. This means all players who connect to and launch the game via TNFS use a shared high score table (and make you feel bad about your skills at Donkey Kong.)
FujiNet is under active development for Atari 8-Bit, Apple II, Commodore 64, Coleco ADAM and other vintage computer platforms with new features releasing frequently. The project is open source, with the core software and hardware implementations being hosted on GitHub.
For more information, check out the FujiNet homepage, join their Discord, and visit the forums hosted at Atari Age.