You may have learned how to build a site with RoR, but have you learned how to be a great developer? I wish I had when I was starting out and didn't get into bad habits.
Do you know how best to test your application?
Do you know how to best deploy your apps?
Do you know how to write good documentation?
It isn't the sexy stuff, and I still don't do enough of it, but I think if you get into these good habits now, the benefits will pay off in the long run (or so I hear anyway).
Though I agree with skrebbel, that if you find something you really want to build, that will often lead you to decisions of what to learn next, I think you can have some more guidance here.
I wouldn't jump into MongoDB and Coffeescript right away. Mongo is a specific tool for specific projects.
I wouldn't jump right into Coffeescript either, I think it is good to know proper Javascript (or some might disagree, but for the most part jQuery suffices at this point).
It looks like you used html5 boilerplate. How well do you understand it? I couldn't tell from the css, are you using SASS or similar CSS tool? I'd recommend that.
Javascript will be very important going forward, and I personally believe that most of my time is spent building front-end rather. Probably 3/4 of my time is spent on css and javascript. I'm building in Backbone now, but putting in and taking out of a database is pretty basic for the most part. I've started doing some NLP stuff, and still, the majority of my time is spent on front-end coding.
Summary, make sure you've got a good foundation for general best practices, spend your time becoming a great front-end coder.
By the ways, I don't understand what showwwwdown is, but you've built a nice looking site.