Photoshop :: Organize Several Thousand JPEGs Into Timestamped Folders?

My sisters photo collection is a total mess without any rational system to it. Its just illogical structured with folders with generic keywords and thousands of files within each folder. For example, there it's a folder called "travel" where she has just dumped thousands of single files from 10 years of vacations. Not the mention the "various" and "misc" folders.
 
What I am trying to do: It does seem like all the photos have the correct EXIF data on them though. So what I'm looking to do is to restructure the collection in folders (with dates taken from EXIF) in a manner similar to this:
 
"/various/filename.jpg" ---> "/2012_06_25/filename.jpg"
"/friends/filename.jpg" ---> "/2012_05_01/filename.jpg"
 
and so on.
 
At least then it gets some kind of chronological structure to it. I want to physically organize the files, not organize them through a database.
 
What is the best approach for doing something like this? I guess I could just batch rename everything from the exif data with Bridge and then organize it from there - but this will still be very tedious. There must be a better way (any PS/Bridge scripts that can do this? The more automated the better. I use Bridge and I dont have LR - but if LR can do this it *might* be whats finally pushing me to buy it.