Now that you have a group of people who all are interested in creating a community garden it is time to develop your vision! The best place to do this is on paper. Remember you will need access to the garden, this means pathways that are wide enough to travel but not so wide that they invite weed growth. It is best for beds to be no more than four feet across so that you can weed them without walking in them and compacting the soil. It will save you a lot of time if you use your water access to develop a drip watering system. So your paper plan needs to include your water source, your beds, and your pathways.
Things to consider include: how many people will be gardening, will everyone have their own bed or will you garden together, and will you be using a rototiller or tilling by hand. I have found that individual beds are the most popular solution. However, in practical experience I have found that new gardeners can be overwhelmed easily with this method. Our garden uses the communal method with a greater sense of community and better production.
With the communal method you will have to decide how to split up the harvest. In our experience this is not much of a problem once the garden comes into full production, early in the season though you need a way to determine who gets that first ripe tomato! The lottery method where every one's name is drawn and they get to choose what they want works well. Most people try to be very fair about what they take home.
Once you have decided how to lay out your garden it is time to decide what to plant. Keep in mind that you will only need one summer squash plant per family but might want three tomato plants per family. It is better to over plant and have excess produce that you can donate than to find you did not plant enough to satisfy the groups appetite. You will likely pick up a few new members late in the season and it is nice to be able to welcome them knowing that you planted enough so that no one feels that they are missing out on something.
You may decide that as a group you would like to focus on heirloom or non-hybrid types of vegetables. This will allow you to save seed for the future. If you decide to try seed saving remember that many things will cross pollinate. You need to plant just one variety or have sufficient space between them. I would suggest that you save seeds from self pollinating varieties and enjoy growing a wide variety. One of the joys of community gardening is growing varieties that you cannot find in your local grocer.
The Seed Savers Exchange and Baker Creek Heirloom Seeds are both excellent seed catalogs. They will mail them out to you for free and it is a great way to find some really fun vegetables to grow. The customer service representatives are wonderful at helping you determine if a variety will do well in your area. Have fun with this part, try something you would not usually buy at the store, half the fun of gardening is in trying something new!