RESTful Java with JAX-RS by Bill Burke. RESTful Java with JAX-RS includes a technical guide that explains REST and JAX-RS, how they work, and when to use them. With the RESTEasy workbook that follows, you get step-by-step instructions for installing, configuring, and running several working JAX-RS examples, using the JBoss RESTEasy implementation of JAX-RS.

RESTful Web Services by Leonard Richardson and Sam Ruby. A great introduction to REST, RESTful techniques, and designing RESTful Web Services.  Its how I learned about REST initially.

RESTful Web Services Cookbook by Subbu Allamaraju and Mike Amundsen. Detailed cookbook on how to design RESTful services.  Subbu has an incredible blog on REST and finally he's taken a lot of his ideas and experiences along with Mike Amundsen and incorporated them into a book.