I have over 100+ old hard drives, ranging from 100MB Quantums to 200GB WDs, most of them PATA, some SATA. Most still working.

The squirrel mentality runs in my family - hoard everything, discard nothing. Thus, and this is a relevant question - any suggestions on how to put these drives to use (anything) instead of them just being deadweights and space takers around the office?

Hopeful objectives and suggestions to keep in mind when you post an answer :

1. Should showcase your geekiness, or plain fun, or serve a social purpose, or benefit the community.
2. You do not need to limit your answer to only one hard drive - if your project needs all 100++, bring it on!
3. Your answer need not be limited to one project per hard drive - if one hard drive can be used for multiple projects, bring it on!
4. If additional accessories need be purchased, make sure they are common. Don't tell me to get a moon rock or something.
5. The projects you suggested should serve a utility, and not just for decoration purposes.