Puzzazz got mentioned on the App Engine blog!

Quoted: Baltic-avenue is an open source clone of the Amazon S3 REST API that runs on Google App Engine

This project allows you to host a "private instance of S3" on top of Google's infrastructure (big table, etc), leveraging existing client S3 libraries and applications - no need to reinvent the wheel.

Quoted: Emulating a long-running process (and a scheduler) in Google App Engine

As previously described, Google App Engine (GAE) doesn’t support long running processes. Each process lives in the context of an HTTP request handler and needs to complete within a few seconds. If you’re trying to get extra CPU cycles for some task then Amazon EC2, not GAE, is the right tool (including the option to get high-CPU instances for the CPU-intensive tasks).

How to identify the current app engine host -- useful if you need to do something on a per-server basis

Quoted: How to identify current host?
There's a very interesting file that should be unique for every server:

>>> open('/base/python_dist/search.config').read()
'datapath .\nsorttempdir .\ndisk /export/hdc3/borgletdata/dirs/prod-appengine.\
mpm_python_dist_v12.apphosting.77627982/bigfiledata/466024'

Didn't read this but it looks like an ok intro.

Quoted: A tutorial on Google's new App Engine, and a sample application which demonstrates the API and database capabilities.

Reasonably decent doc page for Django templates

App Engine issues list, for bugs, feature requests, etc.