The specific wild plants available will vary area by area; make sure you familiarize yourself with local plants such as cactus varieties and mesquite in the dry southwest or fireweed in the Pacific Northwest before foraging.
Because edible wild plants are gathered fresh, they're full of nutrients, vitamins and minerals. There is no such thing as an empty calorie in natural wild foods.
The dandelion, usually seen as a repulsive weed, is almost entirely edible.
Some wild edible plants also have medicinal uses. Plantain is good in salads, and for soothing skin irritation and drawing out infection. Yarrow is good for making tea and also, when crushed, to draw out its oils.
Confident identification is key to safely and successfully harvesting wild plants. Wild sweet pea, for example, looks almost exactly like the delicious and edible eskimo potato plant--but the wild sweet pea is poisonous.
Some wild plants such as nettles must be cooked before eating. Others such as fiddlehead fern, horsetail fern and devil's club can only be safely harvested and eaten when still young and tender.