XOAD, formerly known as NAJAX, is a AJAX/XAP object oriented framework for PHP that allows you to create richer Web applications. It uses JSON and native PHP serialized objects to communicate. Special attention has been paid to security. It supports server side events (observation) and client side events (XOAD Events). Server and client extensions allow features such as HTML manipulation and caching. It is extensively documented, and includes tutorials and examples.
freshmeat.net: Project details for XOAD
I really need to get ahandle on AJAX. Take a look at this example from XOAD. There is a lot of potential in education here. Makes me think that the JS versions of CALI Lessons could be converted to AJAX to get a lot of the Flash features.