Yesterday I was presenting at GeeCON (Kraków/Poland) conference where I showed how you can build Flex apps that run and connect to Google Java App Engine. With my first example I did a simple servlet based RESTful service that was returning XML document to my HTTPService on Flex side.
At the end I demonstrated one of my examples that I previously wrote for Zend_Amf but this time I ported it to slightly modified version of BlazeDS that works with GAE. I used instructions from Martin Zoldano blog http://martinzoldano.blogspot.com/2009/04/appengine-adobe-blazeds-fix.html.
You can give it a try, the app is hosted here: http://flexnotes.appspot.com/
Google App Engine is really immazing technology, hopefully it will be able to run BlazeDS without hacking soon I know GraniteDS and WebORB with their latest builds are already supporting itsource: http://www.riaspace.net/2009/05/flex-on-google-java-app-engine/