Costco once a month for basics: meat, oats, nuts, oils, dried fruit, rice, yogurt, dog & cat food, etc.
Trader Joe's once a week or so to fill in the gaps: milk, spices, snack foods, produce, condiments.
Target every week or two for bread & peanut butter (best prices there), plus guinea pig food & supplies and personal/hygiene products.
Harris Teeter when we need something, bc it's usually most convenient. Or if they have something we love on sale. I used to do a lot of couponing there, but haven't bothered since my daughter was born in November.