swagger.io - Swagger is an open source RESTapi Documentation Tool.
Slate API Docs Generator - Create beautiful, intelligent, responsive API documentation.
Link to QR - Free beautiful QR codes
Doxygen - Generate documentation from source code
Compodoc - The missing documentation tool for your Angular application
Stripe - Online payment processing for internet businesses. Stripe is a suite of payment APIs that powers commerce for online businesses of all sizes. Use Stripe’s payment platform to accept and process payments online for easy-to-use commerce solutions.