Ask HN: Open-source ReactJS applications?

I've been trying to get started with React for a while now but watching and reading tutorials only gets you so far. I still haven't found the courage to start building an app myself. Does anyone here know of any open-source React applications that I could take a look at? I'm mostly still confused about fetching data. React seems to portray itself mostly as the 'V' in MVC and I haven't found much information on "full stack" implementations. I suppose I could combine it with Angular or Backbone. Is the Flux pattern itself similar and worth studying? If anyone can clear some things up or has any applications I can look at, that would be greatly appreciated!