swagger.io - Swagger is an open source RESTapi Documentation Tool.
Zelle - Zelle is a fast, safe and easy way to send money in minutes to your friends and family.
Aglio - API Blueprint renderer
Lydia - Lydia lets you use your card whatever you need to pay, even a friend.
SwaggerGo - The simple way for share your interactive API documentation.
PaymentSpring - The all-in-one, developer-driven payment gateway