Buying organic produce may obviate the need to wash pesticides off your produce, but the recent deadly Listeria outbreak attributed to pesticide-free cantaloupes from Jensen Farms in Colorado makes it clear that we really should wash pretty much all produce – even the ones with a protective skin or rind we don't eat.  Melody Joy Kramer's NPR article Lettuce Learn How To Wash Produce is a good level-headed guide to appropriate techniques for different kind of produce.  Two interesting take-aways:

1. Soaps, vegetable washes or bleach are no better than plain water and appropriate technique.

2. There's no way to clean sprouts — so people at risk (elderly, immune-compromised etc.) shouldn't eat them.