You can dry them by hanging them up in bunches (and don't worry as they soon lose their sting), and drink nettle tea throughout the year as well as using the dried herb in cooking. You can wash, blanch in boiling water for 2 minutes, chop and freeze small packets to give you a regular supply of fresh nettle tops. The minerals contained within are much more readily absorbable than anything that comes in pill form.
At the Urban Fringe, we use nettle tincture for a wide variety of conditions, both as a main treatment ? for some cases of hay fever and eczema, and as an adjunct with other herbs where its anti-inflammatory and diuretic properties make a valuable contribution. Nettles can also help reduce blood sugar levels and stimulate the circulation, making nettle tea a really useful daily tonic to help prevent or delay the onset of many chronic conditions that seem ever more prevalent, such as diabetes and arthritis. We make tinctures from the tops, roots and seeds, as each part of the plant has its own set of uses and indications.
In general we would say respect the nettle. It is a classic medicinal herb, whose main value is in preventative medicine. It serves as a good example for how a good deal of herbal medicine works: by gently restoring many different physiological functions to produce a general improvement in health and well-being. In the hands of a skilled practitioner it can be used more specifically to help cure or alleviate many types of conditions.