If you have a bunch of used dual coil cartomizers (or single coil), you can modify and reuse these as drippers with minimal effort and cost. You'll need just the silicone rubber tip, a couple of inches of resistance wire and wicking material (I use cotton). First step is to remove the tube (rocking it gently back and forth), the filler material, original coil, wire and soldering materials. Next, you'll need to create your coil with short twisted legs. Using the silicone rubber tip, trap one of the legs between the center post and the hole of the rubber tip. Leave the other leg hanging on the side of the rubber tip. Now, put back the original tube making sure that the hanging coil leg is brushing with the tube. That's it. I've modified several of my spent dual coils and all of them are working great.
This is definitely a must try.