Pet projects you build in mid-level languages (Scala, Erlang, Go, etc.)?

A few months ago I joined a Scala shop. I didn't have any Scala / JVM experience before so I've been learning at work. I love programming and very interested to grow in Scala/Akka/JVM stuff so I want to start on pet projects as it's a great way to try, play and learn. It was quite clear for me what pet project I could build say with Rails, but I cannot come up with anything to sharpen my Scala skills. I am checking Github for inspiration and would like to ask you to share what pet projects you developed / developing using mid-level languages?