yaml-cpp naturally splits into a "core" library with two "frontend" APIs, and so that's how the code is organized.
hg clone https://code.google.com/p/yaml-cpp.core/
This provides parsing to the intermediate (and undocumented!) event API, as well as emitting.
hg clone https://code.google.com/p/yaml-cpp.new-api/
This is an upstream of the core repository. It provides the new YAML::Node API. See Tutorial for details on this API.
hg clone https://code.google.com/p/yaml-cpp.old-api/
This is an upstream of the core repository. It provides the old YAML::Node API. See HowToParseADocument for details on this API.
hg clone https://code.google.com/p/yaml-cpp/
This is a mirror of the new-api repository.