Darik's Boot and Nuke
Darik's Boot and Nuke (DBAN) is a single bootable floppy containing the Linux kernel, the BusyBox user environment, and a set of GUI tools for securely erasing computer disks. If you ever need to completely erase a computer (for example, before selling or donating it), you can simply boot off this floppy and scrub the hard drive using various wipe strategies (including the DoD standard method).