TreeSize
This utility accounts for the girth of your burgeoning data, helping you figure out where it could use a nip or a tuck. Open the program from a context menu of a folder or drive to learn the size of the folder and all its subfolders. You can watch the results appear before your eyes. The wasted space can be written up in a printable report, giving you some idea of a pattern for the necessary alterations. This version is FREE. I have been using the Pro version for years tracking wasted space on my hard drive. Download it [here]
As an alternative to this, I really like SpaceMonger. It’s free as well and it gives you a much more visual representation of what’s using your space. Here’s a link:
http://www.werkema.com/software/spacemonger.html