In general, keep in mind that most common, medicinal herbs are not fussy (at least the ones I'm going to suggest below!). Give them reasonable soil, sun, and water, go easy on the fertilizer, and you should do just fine. Now for the herbs!
1. Plantain (Plantago major) - a common lawn weed but great for treating bee stings, bug bites, and small cuts. Make a 'spit poultice' by chewing the leaves and apply to the affected area
2. Comfrey (Symphytum officinalis) - use the crushed leaves and root as a poultice to treat bruises - UNBROKEN skin. CAUTION: Use internally only under care of a professional.
3. Thyme (Thymus vulgaris) - often used in mouthwashes, make a strong tea out of it and gargle
4. Lavender (Lavendula officinalis) - use lavender tea as an antiseptic wash or compress
5. (German) chamomile (Matricaria recutita) - tea from the flowers calms and relieves nausea
6. Peppermint (Mentha x piperita) - tea from the leaves provides anti-spasmodic action to calm cramping, gas, and indigestion.
7. Marshmallow (Althea officinalis) - make a cold infusion of the root to soothe red and irritated mucus membranes
8. Stinging nettles (Urtica dioica) - tea from the dried leaves provides anti-histamine relief to calm allergic reactions. CAUTION: only handle stinging nettle plants while wearing gloves!!!
9. Echinacea (Echinacea angustifolia) - harvest the root at the end of summer, clean and chop before drying. Tea consumed every day will strengthen the immune system
10. Calendula (Calendula officinalis) - tea from the flowers is a mild lymphatic, moving immune cells to where they need to be as well as removing cellular waste
11. Holy basil/tulsi (Ocimum sanctum) - a cousin of mint (and grows like one), holy basil nourishes the hormonal stress axis, modulating release of stress hormones for a more moderate response to stressors
12. Scullcap (Scutellaria lateriflora) - also in the mint family, tea made from scullcap leaves calms the nerves