Today, I'm excited to announce the immediate availability of the second symfony component, the Symfony Dependency Injection Container. This component is one of the core libraries that will power Symfony 2. But you don't need to wait for Symfony 2 to be released to benefit from it. You can start using it today and give us feedback.
As for YAML, the Symfony Dependency Injection Container has its own dedicated website:
The component has already a full book dedicated to it, and a full API documentation.
It also sports a robust test suite with a 100% code coverage as you can see for yourself in the screenshot below.
As for all other symfony products, the component is monitored by the symfony continuous integration server, Sismo, and all the builds are publicly available.