Let's face it: organic produce can get expensive to buy exclusively. Here's a great list provided by The Environmental Working Group which can help you decide how to prioritize your food dollars when it comes to organic buying.
Clean Fifteen Guide to Pesticides in Produce: asparagus, avocados, cabbage, cantaloupe, cauliflower, eggplant, grapefruit, kiwi, mangoes, onions, papayas, pineapples, sweet corn, swee peas, sweet potatoes.
Here's the Dirty Dozen: apples. celery, cherry tomatoes, cucumbers, grapes, nectarines, peaches, potatoes, snap peas, spinach, strawberries, sweet bell peppers, kale/collards.