I also generally end up working on a few side projects every year, a few of them make it to the public eye, most however don't. I also tend to choose languages and frameworks I don't get to experience in my day-to-day as I treat my side projects as learning experiences.
In this vein, I am embarking on a new side project, and I'm quite excited about it. Inspired by this post by Jacques Mattheij, I will build the same application in multiple language/framework combinations. The overall application will be simple (a task list application).
I have a few languages / frameworks in mind, and I'll pick up more along the way. For now, I'm going to build it in Python / Flask, and then score a few metrics and use this as my baseline, as I'm already familiar with both the language and the framework. More soon...