Kawonk DiskFree is an interesting Utility that provides:
Graphical represetation of space on user selected drives on the local and networked computers
System Information
Information from the drives using SMART - such as firmware version, drive serial number, etc.
Drill-down pie charts of folder and/or file sizes for selected drives and folders
Optional right-click integration into the windows shell.
The trial version only works for one drive on a local computer, and does not have drill-down capability
Click on the pictures below for a closer look: