I DoD wipe them then smash them up as best as I can. The latter doesn't prevent data recovery but I figure after it's DoD wiped I'll make it as useless as possible. To physically destroy them they need to be shredded (they have machined that can do it to them like they're paper) or incinerate them.

I wouldn't sell or donate a hard drive that hasn't been wiped first. People can easily pull passwords or PII data off of them.