I'm also not sharing my very best "shopping" spots. Sorry, but I guard such secrets more closely than the elusive magic fishing hole. Some have produced many thousands in savings and I ain't sharing.
Note: none of this is from actual "dumpster diving." That just made a good title. Only "free cycle" bins and thrift stores.
My most recent score was a complete floor to a 9-foot inflatable sport boat, a discarded display model that was too sun-bleached to be saleable, but which had always been on display under cover. Much nicer than the wooden model my boat came with. The timing couldn't be better; my existing floor has just rotted out and I was in the process of pulling it out so that I could copy it! I'll be leaving the patched-up rotting floor in place through the winter, and install the new one in the spring.
- Milwaukee Port-a-Band ($250), barely used. The blade was missing. $5.
- Multiple sets of Gore-Tex foul weather gear, most with the tags still on them. Now we have pant/jacket sets for the whole family, at home, on the boat, and in the car. This particular thrift store gets a lot of high-end outdoor store old model donations. $8-$15.
- New Gore-Tex paddling jacket, very sweet. $5.
- New Perception white water PFD. They mixed it in with the worn-out cheapo horseshoe vests. $5.
- Numerous ropes, cast off by riggers. It's amazing what their racing customers throw away, often replacing good lines after a single season. I haven't bought line in years, I'm spoiled. Free.
- 2-year old skis (K2 ACT old model but new. Plenty of side cut. Were $450, $5 to me).
- Bug netting for my boat, cut from surplus cot bug bar, $3.
- Most of my gas cans, or at least all of the ones I actually use; I hate the new CARB models. Cheap, but that's not the point here.
- Materials. Most of the materials for projects are scavenged, from precast FRP, to metal plates for chain locks and bridle plates, to new wire for solar panels. Mostly from refinery construction projects. I'm spoiled in this regard.
- Fenders. Some are junk, but many are donated or pitched because they are dirty or the owner got a new boat. Generally free.
- Boat hooks. I bought one 30 years ago. Since then, I've found many for free or cheap. I don't even tie them down anymore, they just sit on the tramp, good weather and bad, and I very seldom lose one.
- Luggage. I fly almost weekly, and I refuse to worry over the scratches baggage apes impart. But some fool is always donating a nice roll-aboard with a few scratches; I'm actually quite picky regarding quality, since fall apart luggage is not acceptable. I reason that worn luggage is the badge of a veteran traveler.
- Furniture salvaged for quality lumber, all my own. My modified nav table was cut from a very nice SCAN computer desk that I had no further use for--I still have the original cherry table, in case some future owner prefers it. My salon flip-up bunk was fabricated from the same desk. Good quality teak laminate for free.
- Bike rack. Always available in thrift stores, and easily modified to carrying old non-folding bikes on the stern rail.
- Sheet bags from shoe bags. About $1 each, since several come from each bag. Add grommets in the corners and lash to small pad eyes. I tried the twist-lock canvas fasteners but have found them less durable and versatile.
- Marine antiques. The best deals are found in thrift stores with untrained staff. My daughter's room is collecting some real show pieces, but mostly it's just fun, since each piece has a story. Cheap or free.
Seriously, it's about finding things you actually need or plain materials that can be turned into something of new quality, not about collecting junk. It should be recycling of the very best sort, a very green practice, far better than pretending you're recycling newspapers (which are often processed into absorbents and other nearly junk applications) or bottles (generally melted down) rather than reused as-is.
I spent too much on my new PDQ; I've got to stretch the maintenance and improvement budget to the very limit. My 401-K and my kid's college fund are more important. I enjoy the process of thinking things through, and most of the improvements I've made aren't the sort where you buy some do-dad and bolt it on, adding adding more to clutter than functionality. They are more subtle. Other than the propane heater, solar panels, AC, and davit block installations, very few of my project posts represent more than a few dollars.