Show Folder Sizes in Finder in Leopard and Snow Leopard

By default when using Finder, you can only size the size of files but not folders. At times it can be very useful to see where most of the space on your drive is being consumed.   Having folders sizes tagged to the folders can help this task.

This is my default finder view.

As you can see there is no information for the folder sizes.  To enable this feature, you need to be in either List View or Cover Flow View.  Then select View > Show View Options.  This will present options we can change.  Select the checkbox Calculate all sizes.

As you can see the folder size calculations has started.  That's it!