Platform: All Windows

As a system administrator (or frankly, power home user with big drives), one of the more tedious tasks is managing drive space. Now that we are in an era of half-terabyte drives, giant databases, media files, etc, it's often very difficult to figure out where all that space went. A very powerful visualization tool is the use of treemaps. A typical treemap application takes a data set and represents it graphically, with the size (or date) of data scaled relative to the other datasets. With a tool that does this based on drive space usage, you can quickly locate that 1GB memory.dmp file you forgot about after the last BSOD, or find that .iso image of Windows 2000 you no longer need, etc. A fantastic implementation of this is SequoiaView from the Technische Universiteit Eindhoven in the Netherlands. This free application is fabulous for graphically representing drive space usage on Windows.