I'm trying to write a simple GTD-style todo list app with python and gtk to learn python.  I want a container that can select an individual list from a lot of choices.  It would be something like the list of notebooks area in tomboy.  Not a combobox.
As you can probably tell I'm a beginner and the terminology is probably off.
Can you please tell me what it is I'm looking for and an overview of how to implement it?
You mean a widget to filter a large collection into multiple subsets / views? 
I would guess you have to implement this yourself - a list of options on the left and filtered results on the right, I don't know of any existing (gtk) widgets.
Python PyGTK. What's this component?