http://hollygrovemarket.com/who-we-are
Our local equivalent isn't run on shares or as a co-op. Whenever we want (they're open 2 days/week, and now adding a third day), we can go and either purchase the box-o-veggies ($25), and/or buy items individually (by the bunch/pound). The veggie box usually has veggies, berries, citrus, greens, herbs, rice. The "extras" for outside purchase include milk, cheese; goat milk and cheese; eggs; frozen beef, chicken, and goat meat; locally roasted coffee; grits/cornmeal; bakery products; etc etc etc.
They used to have a trade table next to the veggie box area, where you could trade items out of your box that you might not want for things other people had left on the table. I don't know why they stopped doing it, unless people were just pilfering from the table, or *everybody* left their kale.
Generally speaking, I like the way Hollygrove is set up. My only complaints are that sometimes the produce isn't always exactly what I'd like to eat, that I have to prep it all for fridge storage when I get home (without a kitchen this is difficult, but I'm living in special circumstances at the moment), and the carrots are worthless wee spindly things. But they do put enough in the box to supplement meals for 2 for a week, and otherwise they carry enough proteins, carbs, dairy, and pantry items that you don't necessarily have to go shopping for food elsewhere.