#2: Plantain (Plantago spp.).
Having nothing to do with the banana-like fruits of the same name, this plantain is a common and ubiquitous weed. Its leaves contain natural astringent, antimicrobial, anti-inflammatory, antihistamine, and wound-healing compounds, and they're also brewed as teas for coughs and bronchitis. The plant's seeds are the source of the fiber laxative Metamucil. Chances are you've been walking on plantain all your life and barely noticed it. Look for it along the edge of paved areas or in lawns.
To sooth insect bites or stings, sunburn (or any type of mild to moderate burn), skin irritation, minor cuts, infections, or boils, prepare an herbal paste (also called a poultice): Pick a handful of fresh leaves, rinse off, and mash/grind them with a mortar and pestle or blender, and add a little water to make a thick paste. Apply the paste, and leave it there for at least 10 to 15 minutes (you can cover it with a clean cloth to help keep the paste in place and reduce the chances of staining clothing).
For quick, in-the-field relief, chew up a few leaves (its taste is not unpleasant) and pop the result onto the affected area.
Pastes are usually applied fresh, but can be frozen for convenient later use: drop spoonfuls onto natural waxed paper or a silicone sheet, freeze, and store in an airtight container; when needed, thaw and use immediately.
#3: Chickweed (Stellaria spp.).
This tender, light-green weed is often found in low-growing mats in gardens and fields, even in the winter or very early spring before much else is growing. A paste made from the leaves and stems (see directions for plantain leaves), will help soothe skin irritations, bites, and stings. It is also useful in salads, tasting much like spinach (not bitter like many wild greens), and can be made into pesto or chopped into cooked dishes.