Wiebetech's Drive eRazer is a standalone drive-eraser that you can connect a variety of hard-drives to. It writes one (or more) passes of random junk to every block. I have a small mountain of old hard-disks yanked from machines before recycling, trashing or donating them, and I could really use one of these to blank them before I get rid of them. It's kind of cheezy that you need to buy a "pro" model to run multiple passes on the drive — the only difference between single passes and multiple passes is software, after all.
1. Single-Pass Mode (Standard and Pro Model)
A single data pattern is written one time across the whole disk, deleting blocks including partitions and Host Protected Areas. Verification is also done after a single pass.
2. Multi-Pass Mode (Pro Model only)
The Pro model offers the ability to perform multiple passes. Why? Some studies show that there may be ways of recovering bits of data even after completely overwriting everything on the drive. We believe the laboratory required to actually pull off such a feat would cost millions (if not billions) of dollars. However, if you must convince someone that there's no way data can be recovered, a pro model with the multi-pass feature is for you.