Degaussing the drives may not be thorough enough, given various anecdotes about the ability to recover data off almost any drive using fancy super-expensive equipment.
Unless you've got IBM Deathstar 75GXP's (and if you do, well your data is already as good as gone), your platters are probably metal. Even if you have Deathstars, their platters are glass and are susceptible to the method below:
Metal melts. Magnetic metals lose their net magnetism below the melting point. So find somebody with a kiln, and turn the platters into inert blobs.
You are stuck with these drives. You can't return them for replacement, and if you keep them and still get a replacement, the data is still on the platters. You could just send them to a data-destruction company, but where's the fun in that?