This Cinema 4D plugin allows you to collapse complete rigs into a single object and give them a nice icon. The rig can also be password protected.
PV Render Queue is a free Cinema 4D plugin that allows you to queue render jobs and render them directly in the Picture Viewer.
Here you can find a number of popular Python C-Extensions such as NumPy, Cython and lxml compiled for Python in Cinema 4D.
QuickDocs gives you a list of opened Cinema 4D documents to allow you to quickly switch between them.