We've built a lot on our own. Maybe Senchalabs Connect can help you, otherwise check https://github.com/joyent/node/wiki/modules. Don't know if it's better than devise/cancan though.
Thanks! Just curious, how do you think you would use it?
New features are coming, support for safari, IE9, iPad/iPhone and Android and then make current functionality smarter and better. We will also listen to users so they can say what they want us to focus on.
It's all built on node.js. We used rails before to handle user accounts and static pages but realized we could make it all with node.js and MongoDB instead with some cool template language. :)