Those little green bags that keep fruits and vegetables fresh really do work! I bought a pack at Walgreen's on a whim last week and put my broccoli and lettuce in it. The broccoli I expected to stay fresh, but my lettuce is still fresh and crisp! The label says Debbie Meyer Green Bags and I think they cost $9.99.
If you're like me and you buy veggies with the intention of using them within a couple of days, but life gets in the way and before you know it, it's a week later, then get thee to your local CVS or Walgreen's and buy a pack!