Quick reminder:

Protocol Buffers is a serialization format with an interface description language developed by Google. The design goals for Protocol Buffers emphasized simplicity and performance. In particular, it was designed to be faster than XML.

In other words: Lightning fast data transfer between various parts of a website.

• C# implementation: http://code.google.com/p/protosharp/
• PHP implementation: http://code.google.com/p/pb4php/
• AS3 implementation: http://code.google.com/p/protobuf-actionscript3/
• Wikipedia page: http://en.wikipedia.org/wiki/Protocol_buffers