WinDirStat - a tool for looking at directories

Thanks to a post over on Benjaman Mitchel's blog, I took a look at WinDirStat. A pretty cool program that looks through the folders on a volume and displays the results in traditional directory listing format, but also as set of prettily coloured rectangles sized according to the size of the actual folder. THis is shown on Ben's blog (I'd include a picture here, but it's huge!).