We all need to know the Dirty Dozen. And I don't mean the movie.
I'm talking about this year's list of the 12 fruits and vegetables most likely to contain harmful levels of pesticides, as provided by Environmental Working Group's website. It is strongly recommended that you buy organic versions of these fruits and veggies. Dr. Andrew Weil says he uses the list to do his own shopping, and even endorses it in a video, which is also available on EWG's website.
If you sign up, you can get a printable PDF containing a little cutout for your purse or wallet when you go shopping, which also gives a list of the Clean 15, so you know the least contaminated vegetables. It also includes a more extensive list of 49 vegetables/fruits as well as their rankings in terms of being less or more contaminated by pesticides. And do try to buy organic versions of the worst ones if you can, so that getting your "five a day" will be even healthier.