It depends on where you live. My own survival school offers 3-7 day field courses on harvesting and using wild plants, and I know several other schools that focus on this area of study. If you are on the East Coast, you may want to check out the offerings of the Jack Mountain Bushcraft School as they offer in-depth courses on wild plants. There are also classes offered at community colleges, arboretums, and nature centers throughout the country. I can almost guarantee that there is a botanist or local wild plants expert in your region who teaches so ask around or Google the keyword ethnobotany and your home state to see what turns up.
Two books that will be helpful in your undertakings are:
Chris Nyerges, who teaches edible plant workshops around Los Angeles, has a simple, how-to book that covers the basics and is perfect for beginners- Guide To Wild Foods.
Peterson Field Guide to Edible Wild Plants. This is a good all-around book covering the common edible and dangerous plants found throughout North America. Also, check out the Peterson Field Guide to Medicinal Plants and Herbs.
As I mentioned in a previous posting, some of the more common edible plant resources I have my own survival students gain familiarity with are: dandelion, acorns, pine nuts, and cattails, so consider starting out with these and building on to your plant knowledge from there.