From Mother Jones (http://motherjones.com/blue-marble/2010/03/econundrum-12-most-contaminated-fruits-and-veggies)
In descending order, the EWG's 12 most contaminated fruits and vegetables:
1. Peaches
2. Apples
3. Sweet bell peppers
4. Celery
5. Nectarines
6. Strawberries
7. Cherries
8. Kale
9. Lettuce
10. Grapes (imported)
11. Carrots
12. Pears
For the full list of all 47 fruits and veggies, go here.