Postman - The Collaboration Platform for API Development
API List - A collective list of APIs. Build something.
DreamFactory - DreamFactory is an API management platform used to generate, secure, document, and extend APIs.
Spinneret - Record and Automate Anything on the Web
AWS CloudTrail - AWS CloudTrail is a web service that records AWS API calls for your account and delivers log files to you.
PublicAPIs - Explore the largest API directory in the galaxy