With OS X, you can use Automator to automate several functions. This nifty little how-to by macmost shows you how to sort files into sub-folders using Automator. You can use Automator to alter what happens when a file is added to a folder. In this example, new files added to a folder are then sorted into subfolders according to their type. You can add multiple actions to a folder and then determine which order they are used.
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