Daisy Disk
Daisy Disk gives you a visual breakdown of your disk space in form of an interactive map, reveal the biggest space wasters, and help you remove them with a simple drag and drop.
Discover what's hiding inside the "Other" storage category and clear it up.
Check out the difference between Apple's Storage chart and what Daisy Disk shows:
Very Useful Tool
I found Daisy Disk to be very used to figure out which folders are taking up the most amount of space. Especially useful when looking at external Thumb drives.
You can mouse over various parts of the pie chart to see the largest files in that area.
Daisy Disk also makes it easy to remove files. simply drag and drop files and folder and click the Delete button. Just make sure that you have a backup before clicking on the Delete button!
If your looking to take control of your computer storage, I highly recommend getting DaisyDisk.
Getting Daisy Disk
Daisy Disk is available in the App Store for $9.99 as one of the Essential Apps. There's only 2 Essential Apps in the Utilites category, the other Essential Utility App is Parcel - Delivery Tracking.
You can download a trial versions on the Daisy Disk Website. There are some limited features, and a registration reminder and delay whenever you start the application.