Rick Vanover profiled two different disk wiping tools recently in the TechRepublic gallery. Check out these illustrated guides to using the tools, each of which includes a PDF version. Click the links or images to go to the gallery and PDF.
Zeroing a hard disk with Active@ Kill Disk
How to wipe a hard disk with DBAN
If you have questions about similar tools, or would like to see other tools profiled, let us know in the comments below.