pump.io : Social server with an ActivityStreams API. It's a stream server that does most of what people really want from a social network.
Collage.js : Collage.js brings together many public APIs, along a method of presenting media within a limitless two-dimesional space to create memorable experience...
MailHog : MailHog is an email testing tool for developers:
Configure your application to use MailHog for SMTP delivery
View messages in the web UI, or retrieve ...
Swagger : Swagger is a powerful open source framework backed by a large ecosystem of tools that helps you design, build, document, and consume your RESTful APIs...
Mockoon : Mockoon is the easiest and quickest way to design and run mock APIs. No remote deployment, no account required, free and open-source.
Bluepine is a DSL for defining API Schema/Endpoint with the capabilities to generate Open API (v3) spec, validate API request and serialize object for API response based on single schema definition.