As Jay put it, "All the time...!!!"
I look for free and "underpriced" hardwood furniture with an eye to harvesting the wood for future projects. I find them on the curb, from family and friends, and at thrift stores. I hate to admit it, but sometimes Spouse and I have a small discussion about whether to buy a very underpriced piece of furniture for its wood, or leave it behind for a needy person who might want to buy it to use. I try to be picky - no MDF, particle board, or plywood for me. One problem that happens from time-to-time is that Spouse sees something that I brought home and prevents me from cutting it up, turning it into a restoration project instead.
It takes a certain mindset to be good at harvesting wood from old furniture. You have to be very picky about finding and removing every screw, nail, staple, and other hardware left behind. I don't use metal detectors, just due care. I am ruthless. If there is doubt that some metal may remain (example: broken staple), the piece gets tossed. Sometimes it is easier to cut off a chunk and dispose it rather than pulling out all the metal. I use old cheap blades for the rough cutup work.
I also save and reuse scrapwood. It gets used for prototypes, testing, or backing to prevent tearout. Thin exotic hardwood scraps get laminated into pen blanks. The cutoff ends of pen blanks sometimes get turned into bracelet beads for my nieces. I don't like waste.