Most of these are small-scale, personal or semi-public spaces and communities rather than professional formalized platforms, so please interact with them with that in mind!
Inspiration
Low Tech Magazine - critique of 'net bloat, already-existing utopias
Experience and memories: forums, neopets, personal sites
Resisting Platformization & Professionalization: commercial "platforms" are presented as opportunities to monetize passion work or increase your audience, but they often work in terms of centralizing attention & limiting control
Anti-Professionalism, Open and Collaborative Game Communities: Bitsy
Old Web
Neocities - Building my own Low-Tech portfolio site
Low-Tech Webring - Slow, Low-Tech Site Directory connecting people with similar interests