Tikli is a simple to use microblogging Web application coded in Ruby and powered by Sinatra, Slim, Sass (SCSS) and Coffee-Script.
This was inspired by a project I had to make in PHP (using CodeIgniter). At the time I was studying Ruby, and I thought that it wouldn't be a bad idea to make the same application on different frameworks: Sinatra, CodeIgniter and Rails.
Not only would my language coding experience grow, I would also get important knowledge about the different frameworks' working internals.
It's been coded entirely in Ruby, and it's powered by Sinatra, a great little DSL that makes rapid prototyping a breeze.
Since it's a Web application, somehow it also uses HTML, CSS and JavaScript, through Slim, Sass (SCSS) and Coffee-Script respectively.
From these, I would say that Slim and Coffee-Script really stand out. How they manage to really simplify the flow, the developing process, is absolutely out of this world. Their syntax makes me feel at home.
I can only wish you luck, since Tikli in all of its iterations is mostly a proof-of-concept, aimed at showing capabilities of different tools and methodologies. I would dare saying it could be used as a learning tool!
In any case, have fun: I know I did!