Definitely start splitting up your shopping trips! Like Karen mentioned, get the cheap stuff where it's cheapest: canned tuna 10 for $1 at Save A Lots or Dollar stores. Get your meats on sale (Buy one/get one)--may have to hit up several stores to take advantage of their sales. Produce I would never buy from a grocery store, farmer's markets all the way. Asian veggies are dirt cheap and Mexican stands sell more traditional produce for super cheap. Buy large melons instead of individual fruits like peaches or apples (unless you get a good deal on a large bag of them). You can cut it up into slices/cubes at home (and even freeze it, would taste good on a hot day!).
I can go to the fleamarket on the weekends and buy a week's worth of produce for less than $10. Carrots, potatoes, onions, greens, squash, oranges, bananas, etc. I have to bring a canvas tote bag to fit it all, and my shoulder is hurting by the time I get back to the truck!
Chicken quarters are always cheap and may even be cheaper if you buy them in large packs. If there's a Sweetbay near you, they have a 10lb bag of them on sale for $5.99. Sausage (not links or brats, but the loose stuff) goes a long way and can be used for either breakfast or dinner. Make a giant egg & sausage veggie scramble for breakfast, it could feed you guys for a couple of days!
Buy eggs in flats (4 doz.) instead of individual dozen packs.
Ignacio mentioned making stew, which is an awesome idea. Stew meat is fairly inexpensive, and when dumped into a crock pot full of potatoes, carrots, onions & celery, goes a loooooong way! I make stew in a crock pot and I can't even finish eating it all before it starts to go bad. The dog wound up getting the leftovers this last time. She was a happy girl! Plus there's lots of fat that melts into the rich broth, and if possible I would save some of that broth and freeze it as a soup base for another meal.
The most important thing is not to buy too many lean meats, because that will make it more difficult to keep everyone's bellies satisfied. Plus, the fattiest cuts are often the least expensive!