The Apigility ZF RPC PHP Library helps implementing RPC web services in Zend Framework. Some features include: defining controllers as PHP callables and creating a whitelist of HTTP request methods. The library can be used with Apigility to provide an object model of all captured documentation information and provides a configurable MVC endpoint for returning documentation. Apigility offers JSON representations that can be parsed and used in any mobile framework and allows you to write for the web or native applications simultaneously.
Celoxis is both an online and installable project management platform integreted with Microsoft Outlook, iCal, Google Calendar, and Salesforce.com, among others. Celoxis explains the Celoxis API in a way that suggests they want you to be able to use it easily.