I have a small brass bowl I use for burning herbs on my altar that I picked up for a quarter. I also obtained my Book of Shadows at a garage sale. It's not your usual B.O.S. either, it's an old accounting log book made in the 1930's that was never used and has 2000 blank pages in it. It doesn't have a mystical look to it, but it serves its purpose. I also frequent flea markets.
Booths are full of anything from junk to collector's items.
Don't be afraid to horse- trade with them, but don't expect to find anything cheap there either. Just look around, and don't get excited if you find something you can't live without. They can spot an eager customer a mile away, and will try to talk you into paying way too much for something you can probably find cheaper elsewhere. They are a treasure trove of unique items, such as glassware, brass and even clothing. Most of the time the items are in excellent condition and are very reasonably priced.