The DOD standards for disk erasure can be found at: http://www.dss.mil/documents/odaa/nispom2006-5220.pdf From STB’s Website: nispom2006-5220.pdf
The bottom line for disks with data classified lower than Top Secret is that they may be erased by writing a data pattern to all disk blocks, then writing the complement of the first data pattern to all blocks, then writing random data to all blocks. The STB Disk Manufacturing Module (DMM) test sequence file may be downloaded here : http://www.stbsuite.com/gfx/DiskScrub.zip – download it and you can erase multiple drives simultaneously and quickly with DMM.
What about disks with Top Secret or above data? Magnetic degaussing or physical destruction is the only approved solution.