disposal of old (obselete) equipment

Does anyone have suggestions about how to get rid of some very(!) outdated equipment? I’m talking about 2 working “mini-computers” that the manufacturer has long since been out of business. I suppose they could be disassembled and put in the dumpster but I don’t feel right about the landfill at the end of the line. Anyone locally (central Pennsylvania) that accepts donations doesn’t want these because the proprietary O/S has no commercial value anymore. They have several full-height SCSI drives (at a whopping 328MB each). Each cabinet weighs several hundred pounds, so shipping is likely to be more than the box is worth! Any suggestions?