React Hello World - http://bl.ocks.org/insin/raw/3d28a42c121373950972/

index.html

<script src="http://fb.me/react-with-addons-0.12.2.js"></script>
<script src="http://fb.me/JSXTransformer-0.12.2.js"></script>
<script type="text/jsx;harmony=true">void function() { 'use strict';

var App = React.createClass({
  render() {
    return <div>
      <Hello who="World"/>
      <Hello who="Reddit"/>
    </div>
  }
})

var Hello = React.createClass({
  render() {
    return <h1>Hello {this.props.who}!</h1>
  }
})

React.render(<App/>, document.body)

}()</script>