I've been very happy with MessagePack. It pretty much just does what I want it to: serialize and deserialize things in an efficient, streamable binary format. I

I've been very happy with MessagePack. It pretty much just does what I want it to: serialize and deserialize things in an efficient, streamable binary format. It can be used as a drop-in replacement for a lot of the things that I would otherwise do with JSON. Also, the libraries are very good. It's not often you have similarly high-quality language bindings for Python, Java, and Haskell, among others, but that's the case here.