My refrigerator has become a bizarre experiment in vegetable sociology, thanks to all these tips. I tried @phoenix366's paper towel trick with bell peppers, and they stayed crisp for a week, which is a minor miracle in my house. The aluminum foil wrap for celery worked too, though I initially felt like I was preparing leftovers for space travel. Still, I occasionally mix up which veggies are friends or foes, leading to some tragic spinach casualties.