Last weekend I was driving around and stopped at a yard sale in hope of finding some cool electronics. I was not disappointed. I walked around looking at old radios and other "junk". Electronics at yard sales are often obsolete, but are great platforms for hacking and mods. I walked out with two 120 watt speakers for $3 and an old Super Cub LP RC airplane for $20.
The plane needed some quick repairs, but to my delight worked after duct-taping the nose back on. I am planning on modifying it and adding ailerons and eventually hope to make a UAV out of it using the ArduPilot platform. More on that later.
I think that any DIYer should never underestimate the value of a yard sale. After all, one man's trash is another man's treasure.