I implemented many automation cases based on REST Assured , a jave DSL for testing restful service.
https://code.google.com/p/rest-assured/
The syntax is easy, it supports json and xml.
https://code.google.com/p/rest-assured/wiki/Usage
Before that, I tried SOAPUI and had some issues with the free version. Plus the cases are in xml files which hard to extend and reuse, simply I don't like
