If you don't buy all your foods organic (and many of us can't because it is so expensive) there are 12 fruits and vegetables that should always be purchased organic. They are affectionately called the "dirty dozen".
I have written about the Dirty Dozen before but just came across a very cute and free downloadable "cheat sheet" to help you remember. Created by MyPaperCrane. The dirty dozen are the fruits and vegetables that have a high amounts of pesticides.
I love this little hand guide! Print your own Dirty Dozen Visual Guide from My Paper Crane.
Environmental Working Group (EWG) original Organic Food Shoppers Guide