Chrome Postman Extension
The Postman extension for chrome provides an excellent user interface for testing the REST APIs. Postman supports saving requests to be used at a later time or shared with other colleagues.
This is the utility preferred by the ServicePower development and QA teams
cURL
cURL is a command line tool and library for transferring data with URL syntax and works perfectly for testing any of the REST APIs. While cURL is typically used on Linux based systems, ports are available for Windows.
JSON Lint
JSON lint is an excellent web based tool for verifying that your JSON document syntax is valid. Simply copy and paste your JSON document into the window and click the Validate button.