You could do that on AppEngine already. Just put everything in your static_files directory and set it as the default responder in app.yaml

For more see http://code.google.com/appengine/docs/python/gettingstarted/...

You can use App Engine "supercharged" free quotas plus S3 or Google Storage. Just place a minimal static html file.

http://izuzak.wordpress.com/2009/08/27/how-to-supercharge-yo...

The problem I find with S3 and CloudFront is no restriction based on referrer. It can be addressed with some moving of the files and dynamic HTML but that would kill caching and might break on some browsers.

I was trying to do this last week, and found this: http://drydrop.binaryage.com/ It updates Google App Engine from a github repository. Push your changes, and they're online. It's very easy to setup.