Drop Art Photography Facebook group. Group dedicated to water drop photography (not my group).
DIY Photography has a very good article by Corrie White called The Comprehensive Water Drop Photography Guide. Corrie is one of the leading drop photographers.
Corrie White produced a book on drop photography. I don’t have it but there are many good comments on line. See Corries website at https://www.liquiddropart.com/
Tobias Braeuning has a good article about his set up including the circuit diagram for the device he built (in German).
Kevin Lewis’s PhotosbyKev website has a another good guide (read the comments) called Water Droplet Photography.
Video Tutorial by Daniel Nimmervoll (in German) Wassertropfen Highspeed Fotografie Folge 1
Daniel has several videos on youtube that clearly show the 2 drop method for getting taller sprouts. Start with this one. and then see this one and then explore his whole channel.
Advanced 3 valve Setup by Daniel Nimmervoll (in German) Mein Aufbau für Wassertropfen Fotos
GarethB has an excellent write up (really detailed) on the talkPhotography forum called An Idiots guide: DIY Water Drop Controller with Arduinos and stuff. Gareth goes in to great depth about building a controller. I get an honourable mention 🙂
PetaPixel has an article written by Ted Kinsman called How to Build a DIY Double Water Drip System for High Speed Photos
Bryan Rolfe on Instructables has an article showing how to perform High-Speed Droplet Photography With an Arduino
Wayne Fulton’s scantips website has some very good information on valves, nozzles and drops.
Other DIY Devices
Ramigrafx has another Arduino based water drop controller with full build instructions.
DIY Shutter Release Cables
Here are some of the commercial products you can buy. Most of these are expensive which is why I built my own.