Silent Sifter is a very unique Macintosh software product (US$15, Mac App Store). I've long been recommending that people use heirarchical folder structures for storing images. I personally use PLACE_DATE as my primary organizing principal, but a lot of photographers use DATE_TIME instead.
The question is this: what are you going to do if you didn't use that structure from the beginning? It's a real pain in the butt to go through thousands of images and get them named and stored in meaningful ways that respect such structures. That's where SilentSifter comes in.
The program allows you to point to all your photo file locations and "sift" them, which can involve reorganizing in many different types of structures, renaming files, filtering out duplicates, and much more. It can do the same thing with videos, and it can act as in ingester program, as well. Beyond just files laying around in your computer's hard drive, it can integrate iPhoto, Dropbox, and Google Drive, as well (either to input from or output to in an organized fashion). Moreover, it can be set to continue sifting automatically as you eventually add new files.
The program is definitely worth looking into if you've got a lot of photo files that are disorganized and you're a Mac user.