Evan Coury has posted a quick guide to one of the major features of the Zend Framework 2 project so far - the ServiceManager. He introduces the component and talks about some of its key features.
So, what is the ServiceManager? Basically it's a registry, or container (the proper term is service locator) to hold various objects needed by your application, allowing you to easily practice Inversion of Control. The service manager holds just the information needed to lazily instantiate these objects as they're needed. So if you were thinking 'services' such as those composing a service layer, you might be better off thinking of the service manager more as an "object manager" or "instance manager".
He mentons some of the functionality that comes with the component including invokables, factories, aliases, initializers, configuration classes and abstract factories. He also links to the ServiceManager quickstart over in the Zend Framework 2 documentation for more information.