SequoiaView - SequoiaView is a featured rich application that comes with the visualization technique to provide you a single view of files and documents that are stored in your hard drive.
DiskBoss - A file manager with a focus on storage side of things: Monitoring, classing, storage, duplicate...
DiskWave - DiskWave is a free utility to help you determine where most of your hard drive space is consumed.
Duc - Duc is a collection of tools for inspecting and visualizing disk usage.
RidNacs - RidNacs is a very fast disk space usage analyzer for Microsoft Windows.
Disk Xray - Disk Xray is a disk usage statistics viewer, duplicate files and folders finder and cleanup tool for Mac OS X. Disk Xray performs three fundamental functions, and it performs them great.