I've just learned that there are some shares available in the Roxbury Farm CSA, which I think is the first (and perhaps the only) CSA in Westchester. Pickups are in Pleasantville, Thursdays, 3-7.
I've been a member since the beginning (two years ago) and can't say enough about the quality of the produce, which is all organic. As well as helping to support the farm, you'll get tons of wonderful greens and herbs, lots of vegetables (some that you may not be familiar with already), fruit, and recipes that help you learn what do to with it all. There's also an option for a share from a low-spray fruit orchard, for the fall.
Let me know if you'd like more info!