Scanner

Found nice little app that i believe is standalone, free, and has the open source codes.
Its called scanner and it displays the usage of your drives. Cames in pretty handy sometimes, when i have to fix some pcs and show ppl that there mp3s or video files are taking up way to much of there disk space. Its easier to show them in a pie chart form then in the Gigabytes that they dont understand.

http://www.steffengerlach.de/freeware/

p.s. not sure if it been posted before