Richard Mabey's book "Food for Free" (available in paperback) has loads of ideas, including basic rules for gathering and using weeds and other wild foods safely for cooking and eating. Chickweed, stinging nettles, dandelions, shepherd's purse, common sorrel, garlic mustard - even honey fungus, although you might not want to cultivate that! - are just a few. If it's not too late, you could ask someone to give it you for Christmas.