API List - A collective list of APIs. Build something.
Beeceptor - Unblock yourself from API dependencies, and build & integrate with APIs fast. Beeceptor helps you build a mock Rest API in a few seconds.
Dash 4 - Instant offline access to 150+ API documentation sets
Webhook.site - Instantly generate a free, unique URL and email address to test, inspect, and automate (with a visual workflow editor and scripts) incoming HTTP requests and emails.
Phantombuster - A marketplace of simple to use no-code APIs
MockServer - Easy mocking of any system you integrate with via HTTP or HTTPS.