The Environmental Working Group has published a terrific cheat sheet on the cleanest and dirtiest produce at the grocery store in terms of pesticide residue. It's the perfect size for you to cut out and keep in your wallet.
The Dirty Dozen and the Clean Fifteen are handy lists to help you decide which fruits and veggies you should seriously consider buying organic and when you can get away with cheaper, non-organic produce. If you're interested in the science behind the list, you can read more about that here. (link via the venerable Marion Nestle at Food Politics)