Paul Jones has continued his posts about dependency injection containers versus service locators in his site with this new post that hopes to make it easier for you to tell the difference between the two.
It is easy to confuse a Dependency Injection container with a Service Locator. They are very similar to each other. The differences are subtle. Indeed, it's even possible to use a Dependency Injection container as a Service Locator, although I think it's difficult to use a Service Locator as a Dependency Injection container. They are both sub-patterns of a more generic pattern called Inversion of Control, and some people confuse the term Dependency Injection with the more generic term Inversion of Control.
He starts off with a few questions you can ask to see which camp the implementation belongs in, mostly revolving around how the objects are fetched. He includes some code samples to help reinforce the point, showing both a service locator and DIC. He's also done some looking around at some of the major DIC implementations and which of the two he sees them as (with a few notes explaining his thoughts).