Where does the time go? Anyway, here are some tips I've found:
1- Never shop while you're hungry. You're more likely to make impulse purchases when your stomach is calling for some attention.
2- Stick to your list. I know someone who preferred to shop online: her justification was that she cut down on impulse purchases. Online grocery shopping may not be an option for those who need to purchase a lot of groceries (since it is more expensive). Also worth considering if online shopping is an option for you: Do you gain an extra hour with your family...and how much will you spend on gas to go to the store (versus how much they'll charge you for delivery)?
3- Shop from the top shelves or bottom shelves. A site mentioned that companies have to pay for "prime" positions on the shelves (ie. eye level), which means the tightfisted companies have products less visible. I also saw on many sites: don't shop from the ends of the aisles. Those are usually name brand items that companies pay big $$$ for the placement (and you pay $$$ so they can afford it).
4- Bigger isn't always better. Are you really going to use that 10-pound jar of mayo before it expires? If not, stick to the smaller sizes. Or, shop with a friend and split the products amongst yourselves. Just be aware: bigger isn't always cheaper. Most stores tell you on the shelf tag what you pay per a standard measurement (like $X per pound, or $X per 100 count, etc). Check to make sure you're paying less for buying more.
5- Convenience costs you money. All of those prepared foods (like pre-cut veggies) cost you a lot of extra money. You're better off purchasing raw products. If you can, make it a family project to spend an afternoon preparing all of the raw foods and packaging them in Ziploc bags.
6- Plan out meals beforehand. I'll purchase things the weekend before I plan to eat them...half the chicken in my freezer I've added spices or BBQ sauce into the Ziploc bag so they can go straight into the frying pan or oven. If the Jolly Green Giant can put potatoes, carrots, and green beans in a plastic bag and stick in the freezer for me to throw in the microwave...I can put those same things in a Ziploc bag for a lot cheaper. AND...i can wash the Ziploc bag and reuse it (I am my mother's daughter 
).
7- Buy cheap and freeze. If you can, buy things when they're on sale and freeze them for later. Some people find it's cheaper to have an extra freezer in their home so they can stock up when it's on sale.
8- Try to stick with simple and quick recipes. If you're tired and you've got a complicated recipe in front of you with two hours' cooking time, you're more likely to dial-a-meal or cave in to the "Moooooom, I want McDonnnnnnnnnalds!!!!!!" cries from your kids.
9- Spend with Rewards. If you're going to be spending money, try to get rewards for the dollars you spend. uPromise can be a good way to pay for groceries AND for college. I also have a debit card which benefits local schools; a number of banks have similar programs. There's the old Campbell's Labels for Education program.
I'll try to find more sites with goodies....stay tuned.