K.
You've gotten some great info from the other posters here about which foods etc. to get organic. I just wanted to make a few comments about the organic food industry and organic foods.
1. Check for USDA Organic labeling. Lots of our "organic" food is being imported from mexico, brazil etc now. It may or may not be labeled with the same standards as the USDA organic standard.
2. Local is frequently more important than organic. Go to the farmer's market and ASK the farmer whether they use pesticides etc. Lots of farmers do not, but may not qualify for USDA organic labeling for other reasons (or may not seek the label b/c it's expensive). By buying locally you reduce the transportation costs associated with your food, reduce carbon emmissions, and keep your dollars local. You can also get local food delivered to you through a CSA (community supported agricultur - check out Angelic Organics) or through Freshpicks (www.freshpicks.com).
If you're interested in learning more about where our food comes from (which, I admint, I find fascinating) I highly recommend picking up a copy of "The Omnivore's Dilemma" by Michael Pollen. He is a science writer for the New York Times magazine (most of this book was published as articles in the magazine over the past several years). In particular, I would read the "Big Organic" and "Local Organic" chapters. This book, more than anything, convinced me that I need to put LOCAL as my #1 priority and ORGANIC as my #2 priority
Many consumer groups also evaluate the organic practices of the big agri-businesses. For example, the Tribune published reviews of different organic dairy companies. Horizon (owned by Dean Foods), "O Organics" (Safeway), and Trader Joes (I was surprised to see) scored low. 365-Organic, Organic Valley and several others scored much higher. Lots of big corporate organic producers follow the letter - but not the spirit - of the organic standards, which is why it's nice to be able to talk with the farmer yourself. And lots of companies may have the spirit - but are not technically organic - like Brown Cow yogurt.
That said, better corporate organic than corporate non-organic.
It's tough to find "objective" articles about this as far as health benefits go (the USDA's stance has remained firmly that there's no difference). It's a very charged topic, as you can see. BUT there are clear environmental benefits, not to mention organic frequently tastes a lot better.