Last week I gave a presentation at a local programming meetup. If you are interested in the details (or on React.js) then check out this writeup with the slides and a demonstration app!
Three days ago I gave a presentation on React.js at the TucsonJS meetup. The goal was to provide a high-level overview of what React is talk about why someone ought to be interested in applying it. At the end of the talk I gave a live coding demonstration where we iterated a design for a blogging website (it used WordPress.com for the content generation and management).
If you would like to get started and see what a basic React application looks like, you can check out my react-in-five-minutes repository and dive in (consult the README.md for instructions). The app was designed to be just complicated enough to show how to accomplish real-world problems and yet simple enough not to hide the essence of React in a bunch of logic and noise.