The dirty what?
The Dirty Dozen is a system brought to us by the Environmental Working Group (EWG) to help consumers decide which fruits and vegetables are most important to purchase organic.  They claim that by purchasing the 'dirty dozen' organically instead of conventionally grown, people can decrease the amount of pesticides that they put into their bodies by nearly 80%.

The Dirty Dozen: highest in pesticides
1. Peaches
2. Apples
3. Bell Peppers
4. Celery
5. Nectarines
6. Strawberries
7. Cherries
8. Kale
9. Lettuce
10. Grapes
11. Carrots
12. Pears

The Clean Fifteen: lowest in pesticides
1. Onions
2. Avocados
3. Sweet corn
4. Pineapple
5. Mangoes
6. Asparagus
7. Sweet peas
8. Kiwi
9. Cabbage
10. Eggplant
11. Papayas
12. Watermelon
13. Broccoli
14. Tomatoes
15. Sweet potatoes

Know the Dirty Dozen.
Nothing is worse than wishing you could remember things when you are out running errands, so the EWG has created a free iPhone app that has the Dirty Dozen and the Clean Fifteen.  Not into the iPhone?  They also have a PDF that you can download and print with a wallet-sized card to take along with you at foodnews.org.