Cloud42 is a web application written in Java. It provides both a AJAX-enabled GUI and an extensive Web service interface, allowing you to invoke its functionalities from your own application or from within BPEL processes.
Besides the basic functionalities like starting, stopping and monitoring EC2 AMI instances, Cloud42 offers some enhanced functions like transferring files and bundling new AMIs. Furthermore, it is possible to control your instances remotely by sending arbitrary commands through the Web service interface (or by using the GUI). A notification mechanism following the publish/subscribe pattern allows you to subscribe any endpoint to events that occur on an AMI instance.
Visit the website at cloud42.net for details!