Like a couple others have said, one thing I don't do is buy in bulk as much. I noticed that when I bought the 24 pack of triple-roll toilet tissue, I was really only saving a few cents per roll--not worth it. I buy a half gallon container of milk even though it costs almost as much as a gallon. No problem--this doesn't eat up the savings from not having a car.
My weakness is the produce. It all looks so good at the farmer's market ;that I fill my backpack and tie some bags to the bike. This morning I cooked a huge vat of succotash and that will be my microwavable dinner for the rest of the week. Potatoes, beans, squash, corn, onions, basil....so good!