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.