The Big Mean Folder Machine is a useful tool from publicspace.net (developers of the indispensable A Better Finder Rename 8) that takes the drudgery out of either splitting files into multiple folders or merging files from different folders.
Why would you want to do either of these tasks? Let's say you're trying to back up 30 GB of photographs to DVD. You can either start dragging files to a folder and keep checking with Get Info to see if the folder size is less than the writable size of a DVD, or you can just have BMFM automagically split the group of files into folders that are perfectly sized for DVD burning. Or let's say that you want to take individual folders for former clients and turn them all into one big "Former Client Archive" folder. It's easy to merge all of the files in those different folders into one big archive folder. The Big Mean Folder Machine takes care of file name conflicts in that case.
Version 1.5 adds the ability to create deeper hierarchy levels (dependent on the number of files per level) and restores MP3/AAC functionality. A trial version limited to 100 files is available for download, or you can buy the application for $14.99.