If they're practically ship-able, eBay excels at this. Or, some niche items can be sold on Web forums (e.g., for particular retrocomputing platforms). I also

If they're practically ship-able, eBay excels at this. Or, some niche items can be sold on Web forums (e.g., for particular retrocomputing platforms). I also give away stuff locally, on CraigsList and a nearby university list, and on the curb. (But I never put an item in the "free stuff" category of CraigsList. Always list in the topical category, and don't label it as free in the metadata, even if it is. Too many aggressive flippers and mentally ill people monitoring specifically for anything free, and IME it'll tend to be a big time-waste and a questionable new home.)