And the real fun is that you can grow herbs at home organically instead of paying a premium for organic herbal supplements.
No matter what you try to grow, do your homework. Some herbs may be used medicinally and may be easy to grow, but you need to know which bit of the plant should be used and how to use it.
Foxgloves may be easy to grow and an extract from them may be used in heart medications (fact) but if you don't know how to extract the active principle properly, you could poison yourself horribly easily. The same goes with rhubarb: the root is used as a laxative and a hair dye, the stems are used in puddings and the leaves are horribly poisonous. So if in doubt, don't!
But some medicinal herbs are easy to grow:
Garlic. This needs to be planted in a well-drained soil. It makes a great companion plant to keep pests away from tomatoes (another natural living bonus). Plant individual cloves in midwinter and harvest them in midsummer. You can eat every part of the plant, but the cloves are the best part. Garlic is such a potent herb medicinally that you should inform your doctor that you are taking it - or even eating it raw on your pasta on a regular basis.
Aloe vera: This is more of an indoor plant in England but it grows well in a nice, sunny windowsill. Don't overwater it, as it is a desert plant. Use the gel inside the thick succulent leaves on the skin as an ointment for burns and other skin ailments or as a moisturiser, or eat the leaves as a laxative.
Apples: Not a herb, so much, but the fruit is certainly a good digestive aid (good for treating diarrhoea as well as constipation), as well as being a great source of vitamins and antioxidants. Apples grow on a tree, of course, and need a bit of space plus some regular pruning. Blackcurrants: Another medicinal fruit that's a great source of Vitamin C and antioxidants. Blackcurrants grow from cuttings and don't get too big, so they are suitable for suburban gardens. Birds don't seem to attack them too much - they don't have anywhere to perch while eating. Blackcurrants like a cooler climate and are deciduous.
Dandelion: Herbalists use this herb (or weed, depending on your perspective) as a diuretic and as a general cleanser, especially of the liver. Some people suggest that it can help ease PMS symptoms, particularly fluid retention. Notoriously easy to grow - you don't have to try too hard to get a lovely crop of dandelions in your garden. Both the leaves and the root are used medicinally as a tea.
Peppermint: All mints like growing in damp, shady areas. Peppermint is a digestive aid and to ease migranes and colds. We all know how good menthol (the essential oil of peppermint) is for nasal congestion. While you might not grow enough to make your own essential oil, it's easy enough to grow enough to make your own peppermint tea. Use the leaves dry or fresh.
White willow: Another tree that you might be able to fit into your garden. The inner bark is used as a natural form of aspirin. Willows of all varieties grow very readily from cuttings. Willow trees may even be too easy to grow once you've got them established - more than one gardener or tree surgeon has lamented that willow is next to impossible to get rid of.