The Clover Java SDK by Clover allows API communication to implement payment features into applications. Resources include examples that illustrate app notification, bar code scanner, customer activity, inventory list, and receipt registration.
Yammer, a microblogging-for-business site and winner of the top prize at the recent TechCrunch50 conference, has released an API to allow developers to build their own applications around the service (Yammer API profile). Created by the people behind genealogy site Geni, Yammer has taken the tried and tested Twitter model, which asks users to answer the question "What are you doing?" in 140 characters or less, and adapted it for businesses, turning the question into "What are you working on?"