I have found the most stuff, useful and useless, at estate sales. I have spent so much time driving around my town just looking for older folks' houses that have HAM radio antennae and older television antennae. Whenever they have a yard sale, or if they old man dies and there's an estate sale, hit that house like a SWAT team! Usually the old man has mountains of of old tech lying around everywhere in his garage. I have found countless O-scopes, sweep generators, and buckets and bins of doo-dads. Sometimes the stuff works, sometimes not. When it doesn't, take the parts out or tinker on it til it does. You may have to wait a while, but the payoff is ridiculous.
