Basement Community - A general discussion forum with a few niche topics.
Comfybox - Another general discussion forum focusing more on leaks, hoarding and archival. Very Furry-friendly.
The Midnight Pub - “The Midnight is a virtual pub that lets you write posts and create pages.”
Sheezy.Art - Art website that tries to recreate the highs of pre-2010 deviantart.com and sheezyart.com.
Pixel Joint - A pixel art community that features a submissions gallery and a forum.
Pixel Lounge - “A laid-back pixel art forum with a bit of a focus on dolling and nerd-culture.”
SpaceHey - “A retro social network focused on privacy and customizability.”
Penpalworld - A minimalist and retro social media.
Bitview - A video sharing site that takes inspiration from classic youtube.
The Web Raft - A forum where users can connect and share communities, projects, websites, etc.
Reject Convenience - A small indie-web forum that was recently established at the time of writing. May be a work in progress!
Sudomemo - A revival of flipnote athena, it includes a comment section and a community-led forum in the form of discord and a chat. There is a tab for old games to play!
Webrings and community-like experiences:
The *nix ring - A webring focused on linux distros and foss. Admission to the ring requires some amount of focus on linux in the website.
FurRing - A webring centered on furries. Many versions of the webring exists due to the original webring being defunct.