The Linux Kernel is one of the most complex open source projects. There are a lot of books, however it is still a difficult subject to comprehend. The Interactive map of Linux Kernel gives you a top-down view of the Kernel. You can see most important layers, functionalities, modules, functions and calls. You can zoom in and drag around to see details. Each item on the map is a hypertext link to source code or documentation.
PyFacebook is currently best-tested with Django, and if you are just starting out with Python web development, the author highly recommends this combination :-). If you'd rather use another framework, there are also Pylons and other WSGI helpers in PyFacebook as well.