Matrix is kind of like a federated IRC system and Riot is a web and mobile interface to the Matrix system.
- What is Matrix?
- Matrix doc
- sytest - Black-box integration testing for Matrix homeservers.
- Unofficial list of public Matrix servers
- Matrix GSOC ideas
- Matrix IRCd
- Riot Web - Web client for Matrix.
- Ruma - Matrix homeserver written in Rust.
- Nheko - Native desktop client for Matrix.
- Client-Server API
- Matrix Blog
- The 2018 Matrix Holiday Special
- HN: The Matrix.org 2018 year in review