The Environmental Working Group has put out a new 2010 Shoppers Guide to Pesticides.
Here is a list of 47 different fruits and vegetables that they have tested for pesticides.

They even have a little pocket guide and Iphone app here:
Shopping Guide
Full List

Out of the 47 here is the top 12 worst (most pesticides):
1. Celery
2. Peaches
3. Strawberries
4. Apples
5. Blueberries (Domestic)
6. Nectarines
7. Sweet Bell Peppers
8. Spinach
9. Kale / Collard Greens
10. Cherries
11. Potatoes
12. Cherries (imported)

As acknowledged by the U.S. and international government agencies, different pesticides have been linked with a variety of toxic effects, including:

• Nervous system effects
• Carcinogenic effects
• Hormone system effects
• Skin, eye and lung irritation

Pesticides are unique among the chemicals we release into the environment; they have inherent toxicity because they are designed to kill living organisms – insects, plants, and fungi that are considered “pests.” Because they are toxic by design, many pesticides pose health risks to people, risks that have been acknowledged by independent research scientists and physicians across the world.”