The DocuSign Node.js library by DocuSign aims to simplify the interaction with the API. It uses DocuSign SDK and Database.com to obtain electronic signatures from tax documents, send updated to the finance department, and update the member in the database. Authored by Jeff Douglas on GitHub.
Revel Systems API makes it possible to run a cash register, a restaurant and a mobile point-of-sale system with an iPad as the center of the user interface. Check out what Revel has to say about the API on their website.