Mockable - Quickly define some REST or SOAP endpoints and have them return json/xml (dummy) data.
Mocklets - A HTTP-based API simulator to assist parallel development 🛠️
Postman - The Collaboration Platform for API Development
API List - A collective list of APIs. Build something.
MockServer - Easy mocking of any system you integrate with via HTTP or HTTPS.
Yappes - Build, manage and distribute your APIs in one place 🛠️