"Hello World" App of Flex+Google App Engine+BlazeDS

I've been long time to look some way to develop my sample server host app without a penny.
I registered Google App Engine and Google Site a few years ago, but they both has some limits to start building a site.
Today, after I read this post, I think I may start to build a Flex site, which I can use Flex, Messaging Server and Data Communication Objects. Let's see when I will have my first app posted.