There are a few people running telnet-connected BBSes on the Internet.
kagis
Ah, someone has a list.
https://www.telnetbbsguide.com/
The Telnet BBS Guide focuses Bulletin Board Systems – the original Social Network, serving the BBS community for over 27 years! We list both Dial-Up and Telnet accessible Bulletin Board Systems all over the world. We currently list 976 BBS and related systems with brief and detailed descriptions and a downloadable text-version listing suitable for listing on your BBS or for as a download for others to view and use.
I don't know about number one, but a few that I miss.
freshmeat.net. Announcements of open source software releases and updates.
newegg.com
computer components retailer
is still around, but it doesn't hold the spot it once did.
bash.org. Searchable list of funny, ranked quotes from IRC and similar. There are some archives, like this one.
A few "hosting" sites that went down with a lot of user-created content. No one thing was amazing, maybe, but it produced a lot of dangling links. Geocities: "At least 38 million pages, most written by users, were displayed by GeoCities before it was terminated.[7] The GeoCities Japan version of the service lasted until March 31, 2019.[8]". AngelFire. Tripod. Apparently the latter two are still around in some limited form.
Kaleidoscope.net, a site featuring themes for the eponymous classic MacOS themeing software package. They did a good job of generating theme previews. Fun to browse through.