There are facilities that provide this service. The facilities are often contracted in for facility-wide "shred-days." In house, the military has Defense Re-utilization and Marketing Office (DRMO.) This office attempts to re-sell, or re-utilize equipment safe for use, or is often used in disposition.
Here's what Ive found:
Basically, this is a hammer mill that rotates. Centrifigul force pushes metal "planks" out that shmammer-the-heck out of the hard disk, until it is reduced in size enough to pass through the holes in the filter part of the chamber.
Watch hard drives being Pulverized @ YouTube
Basically, Disintegrating is shredding, but designed for use primarily on plastics such as CDs. This works in a very similar manner to a hammer mill, however it uses blades to cut/shred the items.
Watch paper, plastic, and a CD being disintegrated @ YouTube
Certain hard drives components are melted, such as the aluminum chassis, AFTER the disk has been destroyed through other means.
Watch hard drive melting @ YouTube
I hope this helps!