Turns out that drying them out acts as a preservative (adding them to olive oil simply creates a softer, richer taste) and you can actually make your own in the oven!
“ Sun-dried Tomatoes are ripe tomatoes which are placed in the sun to remove most of the water content. Twenty pounds of fresh, ripe tomatoes will dry down to just one pound of sun-dried tomatoes. Sun dried tomatoes have the same nutritional value as the fresh tomatoes they are made from: they are high in Lycopene, antioxidants, vitamin C and low in sodium, fat, and calories.
Sun dried tomatoes were born in Italy as a way to store fresh tomatoes for the winter. Fresh tomatoes would be dried in the hot sun on the tile roofs as a way to preserve them for the cold months. Today they are still dried in the sun, but in much larger quantities and under strict quality controls.”
Adrian's Blog 