The highlights were lifted verbtaim from this website.. I can't add anything to it. It's spot on, so please read the article to get a good overview of why you should participate in a CSA. Here are some highlights

Community-based agriculture has the potential for creating jobs, developing small business entrepreneurships and keeping precious dollars in the community.

It is important to remember that the industrialized food system was developed at a time when most American businesses were creating systems for mass production and economies of scale.

Because volume is critical to the profitability of this system, farming methods developed to support a large-scale, energy-intensive monoculture that uses huge amounts of water and chemicals for herbicides, insecticides, and fertilizers. Tons of animal waste products also accumulate and pollute land, water and air because factory farming methods keep animals indoors and free of disease instead of allowing them to graze in pastures.

First, local food networks like community gardens, food co-ops, Community-Supported Agriculture (CSA), farmers' markets, and seed savers groups keep money in the community.

I'm starting a CSA Co-op with support from Abbondanza Organic Seeds and Produce. If you want to join this co-op, be sure to purchase a Veggie Share from Abbo and write "West Denver Co-op" on your form. Details of this co-op are still being worked out, but the gist of it is one co-op member (myself) will drive to Boulder each Wednesday and pick up the CSA shares and distribute them. There will be a small fuel surcharge of $2-5.00 each week.

[Note: read Michael Pollan's excellent history of big agriculture here.]