First, the when... check out the calendar at pickyourown.org. For those who really want to support local food and farms- consider joining a Community Supported Agriculture farm.
Next, find your local farmers market, or search by food item at Maryland's Best. Check out their recipes section as well. To see just Montgomery County Specific Markets, check out MoCo's Department of Agriculture. Another great resource is Local Harvest.
What do you do with all that great stuff once you buy local? One Acre Farm has a great collection of recipes.