Are there any strategies for accomplishing this? Is such a relay already available via some sort of Apache extension (or similar)? Knowing C#, my first thought is to develop a C# service application that would run on top of Mono on the Pi. Does that sound like a good idea?
In my specific case, I'm looking to create a HTML5 multiplayer game. I know there are blindingly obvious cheating issues with my proposed implementation, but please keep in mind that this is an experiment, not something serious.