JDiskReport

It also shows you file size distributions, so you know for which file sizes you can optimize your hardware settings (cluster size, stripe size, ...) for.

This app provided me a really simple way to get a comprehensive overview of disk usage. There is an overall overview of disk usage by file type (it is excellent at classifying individual file types; it even recognized my VirtualBox VMs. However it didn't understand git repositories .git tree as one type of file). There is also an overview of usage by directory; both of these combined help you effectively drill down into and safely delete the useless cruft that builds up over time using a computer. I also really like that this is a Java app that will run on any platform, so I can get the same user experience across Windows, Linux, and Mac OS X (previously, I had used WinDirStat, Disk Usage Analyzer, and Disk Inventory X on each platform, respectively). On Mac OS X, I like that it instantly detects when you've deleted a file on the file system so it can update its display. I don't like that you cannot delete files directly from the the app, but this is a minor inconvenience.

Overall, an excellent piece of software that should get more attention!

Beautiful app in it's presentation/visualisation of space distribution.

Bewildering though that you can't launch a directory in Finder/Explorer, or do any dir/file operations.

A nice powerful tool with a great interface.

Not very fat, but works well.
Statistics on long time is a must, binary format of the scan files, unlucky.