Avatar.js

import React from 'react';
import md5 from 'MD5';

class Avatar extends React.Component {
  static propTypes = {
    email: React.PropTypes.string,
    size: React.PropTypes.number
  }

  static defaultProps = {
    size: 32
  }

  render () {
    var { email, size } = this.props;
    var hash = md5(email);
    var src = `http://gravatar.com/avatar/${hash}?s=${size*2}`;
    return React.DOM.img({src, size: height});
  }
}

var is so es5 :-p

I've started using const for everything, unless I need a variable variable, and then there's let. It's only really useful when you do have some variable variables in your code, but it doesn't hurt either way.

const is too long to type, I use let and it makes me feel a little bit I code in ML

Also, why no JSX?

Is it just me or size: height}); needs to be height: size});