I always buy organic dairy produce, carrots, onions, potatoes, apples, tomatoes, bananas and beef. I used to buy more organic produce but I don't feel I can afford it now.
Apparently the levels of omega 3 in organic milk are higher than non-organic milk. I've heard that choirmasters at cathedral schools advise the children to have organic dairy as they think that high consumption of non-organic dairy produce leads to boys' voices breaking earlier. 
I'm noticed myself that children who drink a lot of (non-organic) milk seem to reach puberty and have a massive growth spurt before the average age, but obviously that's just something I think I've noticed - it's hardly scientific. But it does tie in with the choirmasters' observations....
Apparently there have been cases of agricultural workers being sprayed with pesticides while they're working in the fields from the little aeroplanes used to spray.
If I had a bigger budget I'd buy as much organic produce as was available. I've had chronic fatigue for a lot of years and bowel cancer diagnosed at the age of 42. I also have multiple food sensitivities.
I also filter my drinking water through a jug filter. It tastes noticeably better so the cartridge must be doing something IMO! I've heard that people with food intolerances have higher levels of chlorine (blood levels? - summary in a magazine)
Apparently there is a product for washing veg with which claims to remove more of the pesticide residue than just washing with water but I don't know what it's called.