Interesting new open source release from Google called Protocol Buffers. Language neutral data serialization and exchange via protocol definition and generated code for C++, Java, and Python.

Apparently Protocol Buffers are heavily used inside Google, so they look to be a robust implementation. Should be a good format for wire protocols.

They compare it to XML and tout its size and speed advantages. In a client/server implementation, however, JSON is the more likely alternative. I wonder how the size and speed compare.