Elgg

Federated microblogging server.

Advanced forum / community solution based on Ruby and JS.

Delightfully simple forums. Flarum is the next-generation forum software that makes online discussion fun again.

Knowledge-based community software. You can use it to quickly build your Q&A community for product technical support, customer support, user communication, and more.

Forum software built for the modern web.

Link aggregator for the fediverse (alternative to Reddit).