Hmm, I'm pretty sure I have a cast-iron gut compared to most people, but the fact that I'm car-less, poor, and at college means grocery trips are few and far between, hence my discoveries.
(Personal results may vary depending on the individual, plus most of this will taste like crap that's been eaten, then crapped out again, but it IS edible)
Milk: good for about 2 weeks after exp. date (if refrigerated)
Canned goods: excellent for about 3 weeks after exp. date, edible to two months
Bread: Edible until about 12% of it is covered in mold, although the mold WILL give a pretty funky taste
Fresh fruits and veggies: if refrigerated, you can shovel them down about one week after they start to go bad.
Meat: Geezus, even I'm not stupid enough to eat spoiled meat