My husband and I LOOOOVE estate sales. We don't typically shop garage sales because at garage sales, people are trying to get rid of stuff they don't want. There can be a LOT of junk. At an estate sale, people have to get rid of things they actually want to keep, but don't have room for. Estate sales are usually a lot bigger and so you can comb though more things and find what you are looking for faster.
I usually type 'estate' in the search field of the 'garage sales' section of Craigslist to find estate sales in the area. Estatesale.net is also a good place to look for nearby estate sales. The good sales will usually have pictures of the types of things that are for sale.
Last month we went to a sale south of Denver for a couple who was going to a nursing home. It was a large home, and the woman was an avid sewer. When I get old and have to get rid of my stash, I want it to be as big as hers was. It didn't even fit in one room - they had all of her sewing stuff laid out in the master bedroom AND another bedroom. I wish I had taken pictures of it. It was pretty impressive.
There were three tables of fabric that had mostly remnants of a yard or less. I did pick up some interfacing bundled up that was a great price. There were two entire tables filled with thread. I would say half of it was serger spool thread and the other half was $$$ Gutterman thread. There were all different colors. It was a sewer's dream! Then, there were bins full of bias tape, hem tape, piping, buttons, and other notions.
I decided I wanted to beef up my stash of serger spool thread. I grabbed one of the four bins and carefully chose the spools that would be coming home with me. They are 36 in all...or 35. They are kind of hard to count in the bin. Most of them are the Maxi-Lock brand which are $$$ at the fabric store, even on sale. I took the bin downstairs to the table and paid $30 for the whole thing. Because I was buying so much of it, I was able to negotiate down.
Her lifetime supply of serger thread lasted longer than her lifetime, and I bought a quarter of it, so I'm hoping it will last me 10 years.