WhatSize: Helping Nerds Overcompensate Since 1992
Don’t try to hide it — we know you brag about your huge Downloads folder to your online buddies every single day. You know exactly how many gigabytes you have, and probably how many actual bits that translates to. But you want to know more, you say? Well, WhatSize can help.
WhatSize is a neat little tool that can tell you exactly what’s taking up so much space on your hard drive. Starting from a screen that looks very similar to the column view in Finder, you can drill down and see how big each folder and file on your disk is. This can actually be quite daunting, but WhatSize uses a color-coding system to indicate the comparative size of the files and also sorts them with the biggest ones at the top.
Using WhatSize, you can measure any volume or directory. Keep in mind, though, that the bigger the directory you’re measuring, the longer it will take. From my experience, it can measure my entire 120GB hard drive in about three to five minutes, much faster than many of the other file measuring utilities out there. In addition, WhatSize can measure networked drives and even NTFS Boot Camp volumes. There’s a lot of power behind this little application.
There are several other measuring utilities out there, but WhatSize is the easiest to use and the fastest one that I’ve found, and it’s also free. Download it here.

Another cool hard drive monitoring app that I’ve been using is Disk Inventory X. I still like WhatSize for quickly looking at directory structures and finding what needs to be cleaned up.
http://grandperspectiv.sourceforge.net/
grand perspective blows my mind – i was an avid user of whatsize for a long time until i found it…it is faster, and the visualization of your hard drive as colors and size shapes makes it ridiculously easy to find junk, like old downloads you forgot about, old giant files, etc..used it to find and purge about 4 gigs of crap that was buried inside folders…
it is also completely free, and i strongly suggest you give it a look – you may like using them both together, one for visualization the other for straight listings..however, grand has a quick ‘reveal’ option that makes it easy to get the junk out…
[...] though we reviewed WhatSize before, I didn’t realize it’s usefulness until now, when my hard drive started acting [...]
Unfortunately, WhatSize is no longer freeware, it went commercial and became nagware a few months ago …