great topic! CSAs are different per each farm and there's a lot that farms are offering these days. One reader noted that delivery services are different than CSAs, though they may call themselves CSAs. Make sure you are buying directly from the farmer. Some farms buy items like berries or fruit or specialty items like grains from nearby farms, and that's cool but make sure you know where it's coming from.
One long-time good source for finding CSAs and farms near you, or deliver to you is www.localharvest.org - a farmer-populated fully searchable awesome database.