I've found that the tutorials for the Appfuse framework are a great way to get aquainted with the basic features of Spring.
Although they are a few years old, I'd also recommend any of the books by Rod Johnson where he lays out the the Spring design and philosophy: Expert One-on-One J2EE Design and Development, Expert One-on-One J2EE Development without EJB, and
Professional Java Development with the Spring Framework.
The Spring documentation is great and I still usually learn something new every time I visit there. The first few chapters will help you understand some of the core concepts of Spring (i.e. Inversion of Control/Dependency Injection).
Spring Roo is a new project that can help you build the infrastructure for a Spring-based application quickly, but I haven't seen any tutorials for it yet that would help you understand it yet.