On the Zend Developer Zone, there's a new tutorial talking about one developer's method for creating a link between Flex and Drupal to create a data entry form.
Why Flex? Because I'd like to be able to put the widget on any site and Ajax has security issues there. Web browsers, quite rightly, ensure that Ajax pages only request data from their server of origin. So it's much harder to host an Ajax widgets on external sites without kludges like IFrames or Script tag data transit. Flex allows data access from different servers. So it's far easier to write widgets that can be hosted externally.
You'll already need Drupal installed to start working with the tutorial - he chose Mac OS X as his platform of choice, but this setup will work with any installation that supports Flex. He uses the AMF protocol to interface with the PHP scripts on the backend (via AMFPHP) and a small update will need to be made to Drupal to get it to cooperate.
The rest of the tutorial shows how to create the Flex interface - making a simple information form that takes in a user's name, address and phone number and updates the Drupal contact information for them.