You would be surprised how much trash there is in the city around us, that you suddenly start noticing when you have a diy project. Let me share you some moments of my own with you.
I was leaving university campus with my buddies, talking about building magnetic card reader to check contents of my campus library card. Just as I was explaining magnetic heads to one of the guys I see a random cassette player few meters from us, in pile of illegaly dumped trash. Mid sentence I stop, grab and smash the radio open on the curb, pull out the magnetic head and continue talking about the said magnetic head. Guys were bewildered.
At other time I was watching a video about TV fresnel lens based lighting fixture, waiting for my date. After the date while taking the girl to the car I spotted a flat TV next to a dumpster box. Car was right across the street so I took the TV home. She quickly learned I'm no stranger to dumpster adventures. I had the light don't by the morning.
Almost 2 years before that I needed a short (30cm max) ac plug with wire to fix something in the workshop, and I remembered seeing a broken electric tea pot behind our local dumpster while taking out the trash, it was exactly the right length of wire, and awh better than I needed.
Recently, I was renovating something with my wife, and I needed a vacuum cleaner for the drywall sanding and other dust and spills related to that. Just few days after settingy eyes on karcher vacuum I find one in the dumpster as we were walking from the cinema back home. I opened it up next day and realized previous owner had thrown away brand new vacuum cleaner. They had not unpacked and set the filter, hair and piece of cloth got into the air sucking fins and got it stuck. I pulled the trash out, set the filter and voila!
Over the last 10 years I had many more situations like that :)