This is an example of a web blog running on an Google's App Engine. It's not a generic blogging engine but if you want to run your blog on App Engine, you might look at the sources for inspiration. Most of the code could be easily reused since it implements the necessary parts for a blog, like post storage and editing. The code was written by me (Krzysztof Kowalczyk) and is placed in public domain. This code has been tested in real life (http://blog.kowalczyk.info runs on it). It also uses other people's code for doing textile->html and markdown->html conversion.