Beeceptor - Unblock yourself from API dependencies, and build & integrate with APIs fast. Beeceptor helps you build a mock Rest API in a few seconds.
Request inspector - Debug web hooks, http clients
WireMock - WireMock - a web service test double for all occasions.
RequestWatch - Inspect and debug HTTP requests
SOAP/REST Mock Service - Download SOAP/REST Mock Service for free.
Mockoon - Mock servers in seconds