TreeSize Professional - TreeSize Professional is a robust Graphical Manager developed by JAM Software to help you perform different operations on your storage systems like analyzing the data, organizing and freeing up the storage system effectively, and viewing the usage.
Disk Inventory X - Disk Inventory X is an open source disk space analyzer and disk management tool for the Mac OS X operating systems that allow the OS X users to check for the availability of free space in their machines.
SpaceSniffer - SpaceSniffer is a freeWare (donations are welcome) and portable tool application that lets you understand how folders and files are structured on your disks.
Space Gremlin - SpaceGremlin is aimed to discover essential and extra files to delete from a hard drive.
TreeSize - TreeSize tells you where precious disk space has gone to.
Baobab - Distributor of workload automation, financial statement reporting, data access, IT Asset Management and Service Desk software solutions.