ClickBank PHP Sample Code by ClickBank. Demonstrates how to interact with the capabilities of the API that include request refunds, request cancellations, and retrieve a list of transactions in a ClickBank account. Note that the API is for use for those developers in advanced stages, according to ClickBank.
iDreamBooks, book review aggregator, deems itself the "rottentomatoes.com for books." iDreamBooks searches reviews across media outlets and compiles the data to a single, comprehensive repository of review. iDreamBooks offers developers access to the reviews through the iDreamBooks API.
Campaign Monitor, the email marketing software aimed at designers, recently announced a massive API update that is sure to please developers. The changes are less of an update and more of a complete redesign from the ground up. The folks down in Sydney have gone RESTful, the new version no longer supporting SOAP. The API also added realtime tracking and integrated powerful segmentation tools.