WOW! Haml is making in-roads to JSON! jQuery-haml is a Haml-like language written in JSON. This allows for easy DOM building so that web apps can do more work independent of the server for a better user experience.
You can see a small example page using it at http://static.creationix.com/jquery-haml/examples/index.html. View the source to see that all the content is built after page load.
To be clear this project was recently split. The server-side half of the component stayed at the old name of haml-js and has it’s own documentation and everything there.
Similar to Sinatra and uses Haml-js. Looks like things are heating up for Node.js.