IPFS I'm really glad things like nerdctl and guix support it, but I wish more things too advantage of the p2p filesystem.
Petals.Dev and hivemind ml P2P AI inference and training seem like the only true viable options to make foundational models that are owned soley by authoritarian government s and megacorps.
Matrix for federated general real time communication. (Not justs chat, video, images, but just data, with third room being on the cooler demos for what is possible)
Activity Pub for asynchronous communication between servers. The socialmedia aspect is obviously the focus and the most mature, but I'm also excited for things like Forgejo (Codeberg.org) and Gitlab's support.
I am also excited for QUIC for increased privacy of metadata and reduction of network trips.