This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
There are other books available, but these are not free:
J2EE Web Services - Richard Monson-Haefel (good introduction, but skip parts on JAX-RPC and UDDI)
Java Web Services Up and Running - Martin Kalin
If you do not already have experience with XML, you should study it prior to reading anything else - it is a very important basis for web services with both JAX-WS and JAX-RS.