Windows only: Drive space visualiser utility SpaceSniffer takes the mundane task of cleaning up your drive and makes it more pleasant with some impressive graphics.
SpaceSniffer works similarly to previously mentioned SpaceMonger—it provides a drill-down treemap view of your drive so you can quickly identify where your drive space has gone. The difference is that SpaceSniffer does it with style—drilling down into a directory with an animated zoom effect that makes it a lot more pleasant to use.
SpaceSniffer joins a very large group of similar utilities—you can take your pick between: DriveSpacio, Windirstat, Free Disk Analyzer, Primitive File Size Chart, Xinorbis, Simple Directory Analyzer and Treesize Free—all of which do the exact same thing with different graphical interfaces: they help visualise your hard drive usage. There's no right answer between the different utilities, you should use the one that works for you.
SpaceSniffer is a free download for Windows only—but instead of visualising your drive usage all the time, you should learn how to use Belvedere to automate your own self-cleaning PC.