JunoRestClient!

Postman helps you be more efficient while working with APIs. Postman is a scratch-your-own-itch project. The need for it arose while one of the developers was creating an API for his project. After looking around for a number of tools, nothing felt just right. The primary features added initially were a history of sent requests and collections. A number of other features have been added since then. Here is a small list.

Eviware, the maker of soapUI, Web Service Testing Leader

The web developers helper program to create and test custom HTTP requests.Advanced REST client for Google Chrome.

Debug APIs like a human, not a robot.

Runscope helps you monitor, log and measure API usage to solve API problems fast. Automatically monitor APIs without any coding. Runscope provides complete logging for all of your API traffic. Track down troublesome API calls with powerful search. Debug problems by peering into the details of every request and response. Works with any public or private API, behind the firewall or in the cloud.

A REST client for almost any web service (Firefox and Chrome extension).

APIs are essential to every online business. StopLight helps companies manage their API lifecycle. Our visual modeling solution removes the massive amount of manual effort needed today, and instead reduces friction, and improves efficiency, across all API stakeholders.

REST Client for Android is a development tool used to test RESTful web services. Features include:

A Simple Windows application to help developers debug REST based services.