I started using marty.js [1] after it popped up on HN a few days ago [2]. The documentation is outstanding and includes guides/explanations of the architecture beyond just an api reference.
+1 for Marty. I'd never used Flux before, but had made some small apps in React and felt pretty comfortable with it. The Marty docs have a particularly good description (with small examples) of what each piece of the Flux model is supposed to do. After following those and making a toy project, I actually felt like I'd wrapped my head around the basics of Flux+React pretty firmly.