Onion is a microframework for web applications in python. It was inspired by a discussion on pylons-discuss mailing list that suggested using WebOb as a basis for framework instead of pure WSGI. This framework is deliberately very simple and is not intended to be a complete, full-stack framework.
onion.simpleapp module contains some preconfigured components that are less flexible, but should be a sufficient base to start writing your own application.
It can be downloaded here: http://squarewheel.pl/onion/download/current.tar.gz