Rosemary is one of the easiest spices to acquire for free, since it is used so widely in home, corporate and city landscaping. In some places, it grows wild. Rosemary is a sturdy plant in the mint family that makes solid, fragrant bushes, stays green all year, and grows almost anywhere.
When scouting out a source of rosemary, try to find a bush that is relatively clean. For example, you may not want to use a roadside bush that is along a very busy highway, or one used for landscaping at a dog park. If your neighbor has a bush, you can ask if they will let you take a few branches. While the law states you can take food from plants that hang over public areas, it doesn't hurt to ask your neighbor first.
Clip rosemary branches near the top of the bush, in case the plant has been used by wandering dogs. Take branches that are not in flower, for the best flavor.
Since a little rosemary goes a long way in cooking, you will really only need to take a few foot-long branches at a time. You won't want to denude the bush in any case, since one of the rules for foraging is to leave plenty for others. Be discrete in your collecting.
Take home your rosemary branches and wash them under clean cold water. This will rinse off the dust and be a help if the bush was exposed to pesticides. Shake off the excess water and spread your branches to dry overnight on a clean towel.
Once your rosemary is dry, tie the branches together at the base with a bit of string, and hang the bundle somewhere in your kitchen, pantry, or root cellar. A dry, dark place is best for long term hanging. You can use the leaves immediately by clipping them from the woody branches as they hang, or you can wait until the leaves are dry and crumbly, and then place in jars.
Rosemary is a wonderful spice to add to stews, soups, meats, bread, potatoes or vegetable dishes. It also makes a pretty garnish. Small branches are lovely placed in a clear water pitcher and add a fresh, minty note to beverages.
You can also make a tea from Rosemary; the Wikipedia relates that Rosemary is full of antioxidants and is potentially anti-carcinogenic. Rosemary has astringent qualities that make it nice added to handmade soap and other toiletries, can be added to floral arrangements as greenery, and can be used to flavor oils and vinegars as inexpensive 'gourmet' gifts.
Rosemary resources from Amazon -
Growing & Using Rosemary: Storey's Country Wisdom Bulletin A-161
The Wild & Weedy Apothecary: An A to Z Book of Herbal Concoctions, Recipes & Remedies, Practical Know-How & Food for the Soul