I was cleaning out my computer room last week and collected up about a dozen HDDs that were too small for my needs. They ranged in size from 120GB to 2TB. I really had no use for them any longer since my backups take more than 2TB (have lots of media files). It was frustrating since they were all perfectly functioning drives that I simply had no use for. I considered selling them but have tried to sell used drives in the past with little luck. I was about to toss them into the electronics recycling bin but a friend said he wanted them so I gave them to him. They're now his problem.
My point is, either put them in external cases and use them for backup purposes as suggested above or get rid of them. Don't hang on to them thinking one day you'll have a use for them.