I hink the best bargain I found for sewing was over 3 yards of a lovely large rayon check fabric. I simply hemmed it and turned it into a tablecloth for spring. It was $1!
Another find - not associated with quilting - was an applebox full of yarn: teal, fuscia, brown, black, and some white. There was also a few skeins of sweater yarn. I used everything but the sweater yarn to crochet a REALLY long (7 foot) stripey sofa blanket last winter. My husband loves it. Our calico has figured out that if she sits on it, she can have all 7 feet to herself and not have to share with the people. :-o
Quilting-wise, I found some really great notions, velvets, lace, and obscure patterns at an estate sale. I got 5 yards of lace for $3, 6 yards of plush velvet (the really high quality rayon kind) for $5 and a box of assorted notions like binding, hem tape, uphosltery needles, etc. for $1. My husband couldn't believe it when I walked in saying I wasn't going to buy anything and I blew a $10 bill. :)