Omni Disk Sweeper

All MAC owner's should have this installed.

http://www.omnigroup.com/products/omnidisksweeper/

This program allows a user to see similar to what they see under "storage" in the about Mac menu.

The difference is that it shows you each folder and how much space without having to right click. It will tell you what is taking up mad space.

For me, Mail.app was getting crazy. It was storing a crazy amount of stuff on the HD and I was like where is all my space going. 0kb would show for usage and only "Other" was highlighted as the culprit using all the space, which was incorrect. It didn't show music, movies, pictures, videos, etc. It saved my Mac recently. One day a pop up said my HD was almost full, I knew it wasn't anything I've done.