After years of moving around books in the attic, I discovered that I could list them on Amazon for free. Unfortunately you will see that the novels and bestsellers you purchased for real money will be offered for 99 cents.
I don’t understand how this is profitable to the seller. Amazon lists the book with your description and your condition rating and adds a postage rate. When the sale is complete the buyer rates the transaction and the seller gets the money and postage minus Amazon’s take. It’s quite easy and I had one great sale of a $50 book on image processing that ended up going to an image processing business. Everybody won in that transaction.
If you have some big (unable to mail) stuff like a used car, old roof racks that only fit cars or vans with rain gutters, hiking boots that don’t fit, the ubiquitous exercise bike that you are using as a coat rack then I would suggest Craigslist. Once again the posting is free but you need to arrange for the transaction. This is more prone to scams and weird emails so you need to be a little more careful. However I was able to sell a used car, those uncomfortable boots,
the roof racks and a mosquito magnet device that was completely ignored by New Hampshire mosquitoes. In full disclosure, I explained this to the couple that bought it but they were willing to give it a try (but I sold it for cheap!). Selling on Craigslist is a bit like having a yard sale. You let the folks know via email where you live so you need to be careful before releasing any information. I got one questionable email from Florida about someone who was going to send an agent because they had been waiting all their life to purchase a run down car. Usually people in the salt-belt of New England want to buy “Southern Cars”. I could imagine getting a “bank” check made out for too much and being asked to “refund” the difference or some other creative scam. I ignored this one.
We had a couch that ended up in the landfill (which cost me $25). I tried everything to unload this. First I listed it on Craiglist, then I offered it for FREE on Freecycle. There were many interested buyers but the problem always came back to transportation. Freecycle is a great resource for getting rid of items that are still usable but really not saleable. I had a pile of classical music vinyl records that I “rescued” at the dump. I intended to digitize them. Digitizing vinyl in real time was never going to happen. A nice couple arrived and took them away. They used to have a radio show. I kept music out of the landfill. This is very fulfilling.
Finally for valuable stuff (like my pile of film cameras) there is the grandaddy of selling sites eBay. I was able to sell one of the cameras for more than I expected. Ebay offers extensive help on the selling process and I was happy with my experience. They take their cut but the site is probably the most well known (and visited) of the one’s I have listed.