One word: Aldi. I save so much money shopping there it's not even funny. True, they don't have as wide a selection as other stores, so I still have to buy a lot of my diet-type foods elsewhere, but it's dirt cheap, and they are always adding new products including LF, FF, and SF products. And here's an insider secret for you (my mom was a manager): a lot of their food is brand name food repackaged (e.g. Campbell's soup and Heinz ketchup), so the quality is still good.
I'm not aiming for skinny, I'm just aiming for happy.