FWIW, the sample application I built to familiarize myself with GAE is
a simple REST cache. It's written in < 250 lines overall, including
Python + YAML.

For instance, a resource such as:
http://www.ncbi.nlm.nih.gov/entrez/eutils/esummary.fcgi?db=pubmed&retmode=xml&id=3966282
can be accessed via GAE using:
http://libxcache.appspot.com/get?url=http%3a%2f%2fwww.ncbi.nlm.nih.gov%2fentrez%2feutils%2fesummary.fcgi%3fdb%3dpubmed%26retmode%3dxml%26id%3d3966282

Or, you can access:
http://demo.jangle.org/openbiblio/resources/5974
as
http://libxcache.appspot.com/get?url=http%3a%2f%2fdemo.jangle.org%2fopenbiblio%2fresources%2f5974
(To take some load off that Jangle demo, Ross, in case it's slashdotted.)

 - Godmar