I agree with DeMo, though I have heard of YAML. I wouldn't use it in a web project though, and the language I do use apart from PHP doesn't have a binding. So I can't/won't experiment with it.
Edit: Let me rephrase that: it kinda has a binding, but it's either incomplete or unstable on roughly 25% of YAML's features.
__________________ Programmers are in a race with the Universe to create bigger and better idiot-proof programs, while the Universe is trying to create bigger and better idiots. So far the Universe is winning. - Rich Cook
Why not use JSON instead of YAML? They both have data serialization as a goal, and JSON is much more easier and closer to the concept of "human readable computer code". Although YAML is much more complex (has data types and some advanced features from what I've seen on the Wikipedia page) if I'd need data serialization, I'd go for JSON.
I have optimistic thoughts, even though sometimes (if not always) life's a bitch.