Hyper-G, commercially now Hyperware was for a dashing moment the competitor to the web as we know it (University of Graz). It provided a system where you couldn’t get dead web links, still built on http:// but speed to market prevailed.
One to watch http://tent.io – this could be one to watch – FaceBook 🙂 It could certainly replace email in the near future very rapidly.
For medium techies, here’s another person’s take: http://web.appstorm.net/general/opinion/why-tent-io-seems-more-promising-than-app-net/