I've been hoarding Martha Stewart magazines for the past six months with the idea that before I recycled them I would go through them and pull out recipes, crafting ideas, etc. I found this great visual on what fruits & veg have the most / least pesticide residue.

Dirty Dozen (fruit / veg to buy organic):

• Peaches, Apples, Bell peppers, Celery, Nectarines, Strawberries, Cherries, Kale, Lettuce, Imported grapes, Carrots, Pears

Clean 15 (fruit / veg OK to buy conventional):

• Onions, Avocados, Corn, Pineapples, Mangoes, Asparagus, Sweet peas, Kiwifruits, Cabbages, Eggplants, Papayas, Watermelons, Broccoli, Tomatoes, Sweet potatoes