all you need to do is cut your tomatoes in half, sprinkle with salt lay them out on a tray in a single layer and leave them out under the intense sun until they are dry. Should take anywhere between 4-14 day depending on intensity of the sun. Also, cover with cease cloth to ensure no bugs or critters get in there:) for more details check out this link:

http://homecooking.about.com/od/howtocookvegetables/a/sundriedrecipe.htm