What are the best tools for testing web services with REST protocol and JSON data format? [closed]

Answer 1

A nifty framework/library for testing REST with json is "rest-assured"
http://code.google.com/p/rest-assured/

Inspired by BDD and Groovy ( but it's Java ) it makes it easy to test REST resources

given().
        param("key1", "value1").
        param("key2", "value2").
expect().
        body(containsString("OK")).
when().
        post("/somewhere");

And it's easy to work with JSON path

// Example with JsonPath
String json = get("/lotto").asString()
List winnderIds = from(json).get("lotto.winners.winnerId");

Getting started is easy.
http://code.google.com/p/rest-assured/wiki/GettingStarted

Disclaimer
rest-assured is founded and managed by the Company I work for.