Freeing Up Disk Space

I'm trying to free up some hard disk space on my MacBook Pro. According to Disk Utility my total disk space is 111GB and I've used 86GB. But when I calculate the disk space I've used by adding up the size of all my folders eg. movies, applications, documents etc etc, these folders add up to only 27GB. So I don't know where or how the extra 59GB are being used.
Is there an application in MAC which lists all the files and their sizes on the hard drive so I can see exactly where these 'missing' GBs are being stored?

THANKS

Disk Inventory X will let you see visually where all the files on disk are

Disk Inventory X

I HIGHLY! recommend getting X-Slimmer. Its an app that slims down all the files on your system by removing the Power PC parts of them.

You have to purchase the app but im sure there is a way to get it for free, cough* cough*

Heres the link to the site : Xslimmer - Your Mac, on a Diet!