A great, cheap herb treatment turns out to be an old, old food preservation technique. We have a couple of rosemary plants that were getting quite large (well, at 2 feet, large for an upper Midwest window box in a west facing window). I recently read that 4 parts ground herb plus one part salt would preserve almost any green herb. It seems to work quite well, so far.
The part that amazed me is the flavor. I actually like it better than fresh rosemary in some ways. As the salt draws moisture from the rosemary, the oils are left and heightened. It's kind of like rosemary++. The only down side is that it is 1/5 salt and not appropriate for everything, but the rosemary plants are still in the window
The reading came from "Preserve Everything..." by +Leda Meredith