I don't think I saw anyone mention this: mushrooms. People with shaded, steep, or forested land may not be able to grow a more traditional garden, but growing edible mushrooms is actually really easy. It's a great medicinal food source, and it turns wood into awesome soil. Find younger trees in your forest, preferably with a 4-6" diameter, and cut them into 3-4' sections (thinning the forest responsibly won't damage it, but instead will provide opportunities for nearby trees to access more resources and thrive). For very little money, you can buy yourself shitake, oyster, or other spawn from a supplier like Field and Forest plus a few basic tools for inoculating. Invite some friends over and inoculate a whole bunch of logs in a day. Although it takes a year to 2 years for the logs to start fruiting, they can provide you with edible mushrooms for 4-10 years depending on the size of the logs. There are also other methods for inoculating, like the totem pole method where you use larger pieces of logs set on top of each other. Also, if you have any trees cut down and generate woodchips, you can create mushroom beds to grow winecap mushrooms (winecap spawn can be bought from the same suppliers).
Once you get a good supply going, you can sell them for quite a bit of money to local restaurants - a great cash crop.
Michael Judd's book Edible Landscaping with a Permaculture Twist has a chapter on growing specialty mushrooms that is extremely helpful and easy to follow with lots of photos:
http://ecologiadesign.com/2013/07/03/new-book-on-edible-landscaping-by-ecologia/
Plus check out the Field and Forest site:
http://www.fieldforest.net/
