Apiary - Collaborative design, instant API mock, generated documentation, integrated code samples, debugging and automated testing
APIsentris - Build APIs instantly from MySQL, PostgreSQL, Google BigQuery and more
Clearbit Salesforce Prospector - Quickly build targeted lead lists directly in Salesforce
API List - A collective list of APIs. Build something.
API Blueprint - A powerful high-level API description language for web APIs.
Transposit - Build API-dependent applications effortlessly