At RubyConf Br among several interesting presentations there was at least 3 topics mentioned on most of them. It was not a coincidence that the best Rails developers in the world was talking about the same tech things, these topics seems to reflect the main trends on web development nowadays.
Distributed (systems) applications
Two way communications
Client side apps
Several years hearing about distributed applications and now Rails seem to bring it seamless to everybody. Some speakers like @apotonick, @dterror, @mloughran talked about it. You should scale your rails applications horizontally, you can build a new app for almost every feature in your product.
Those apps can live completely separated communicating each other with solid RESTful APIs, try roar gem to facilitate your work.
Or you can use Engines to load apps inside other app and share its resources.
Social media stream, live chats, delayed jobs are some of the goodies of web 2.0 apps. Those things would never have a great user experience without a two way communication system. Something that was brought to us by HTML 5 with web sockets and can be used to build better rails apps trough EventMachine. Wanna start using real time events in 10min? Try pusher.com.
If you do live in earth you already heard about node.js, coffescript, backbone, or some other client side app library. Afterall, with distributed app and real time HTTP response, all you need to bind it together with a great user experience would be a great client side app. You can find some examples on @rodriguezartav’s github.