Org mode does not require TODO lists to live in separate documents. Instead, TODO items are part of a notes file, because TODO items usually come up while taking notes! With Org mode, simply mark any entry in a tree as being a TODO item. In this way, information is not duplicated, and TODO items remain in the context from which they emerged.
Org mode providing methods to give you an overview of all the things that you have to do, collected from many files.