Unmount busy drives

Ever tried to umount some storage device which kept being "busy"? Well, this is the way to find which program is keeping it busy:

lsof +D /mnt/windows

This will return the command and process ID of any tasks currently accessing the /mnt/windows directory. You can then locate them, or use the kill command to finish them off.

source: http://www.tuxradar.com/content/linux-tips-every-geek-should-know