There's a whole family of sites based on the same codebase of everything2 (which was a cousin of the /. codebase).

https://everything2.com/title/Everything+Engine

Aside from E2, it is likely that PerlMonks is the other still active site - https://www.perlmonks.org ( https://en.wikipedia.org/wiki/PerlMonks )

The others seem to have fallen into disrepair if they are still up at all.

h2g2.com is a another user-edited encyclopedia site which is almost, but not quite, entirely unlike e2. It launched about a year after e2, and about two years before wikipedia.