The use of API's (Application Programming Interfaces) as a means to access previously siloed information for use in applications and projects is increasingly dramatically in popularity. Many companies are releasing their own API's in the hopes of getting developers to mashup and integrate data into their own projects. Below are three API's released this week that are certainly worthy of note:

FormSpring has created an API to enable programmers to add, edit and retrieve data stored within their FormSpring account and currently returns data in XML, JSON and serialized PHP. The full launch of the API is scheduled for mid-September.

iWebTrack Holdings Inc. launched an API-based private-label/branded reseller program that lets partners resell iWebTrack’s service to their customers under their own private label.  Those seeking business opportunities can partner with iWebTrack and own their own turn-key, web analytics business, with complete back end and billing integration for as little as $400 a month.

SharedBook has launched an Open API Challenge to encourage development of extensions from third party applications that flow text, photographs or other content into SharedBook’s Reverse Publishing Platform for on-demand output. SharedBook’s API allows you to integrate online content into a structured book product that can be previewed and purchased, or personalized further.