The Postmark FeathersJS SDK by feathers-plus allows developers to integrate the Postmark API into their applications built with FeathersJS, an open source REST and realtime API layer. This SDK is installed via npm.
BetterWorks announced an API that connects data points from across an enterprise into a single report, dashboard, or method. The API enables companies to gather the data necessary to create and measure company goals. BetterWorks aims to "combine the power of goals and the value of people".
Email-list.com provides email marketing and social media tools for businesses. Recently the company announced an Email List API that gives visitors to your website access to counts and quotes on email lists.