WinDirStat: Windows Directory Statistics

I like Directory Report
It looks like the MS-Explorer but shows folder size in bytes
No confusing colored blocks
http://www.file-utilities.com

WinDirStat is a most powerful tool to find disk space and to visualise how your disk is being used.

The treemap display will wow even non-technical friends and family!

I used to use SequoiaView, but this application is better. It scans your drive(s) and builds a tree structure that lets you easily drill down to figure out what's eating your disk space. It also generates a treemap (I understand the term, but there's gotta be a better name- the visual looks nothing like a branched structure) that looks almost identical to SequoiaView.

The bottom line: This Windows application does one thing, show you what's taking up space on your drives, and does it very well.