DryDrop is an interesting little app: you use DryDrop and Github to create on GAE a site that will hosts a static web site that refreshs automatically when your Github repo is updated.

So basically, you use DryDrp to create a GAE web site.
Then host your git repo containing your static web site on Github.
Then link the two and your GAE will have a cached static site for free (as long as you stay in the free tier of GAE of course).

Quite nice.