Some time ago I sold on Tindie the prototypes of servo shields compatible with the D1 Mini boards. Afterwards, there was so much interest in them, that I decided to try and make a larger number of them. I learned from my mistakes, and improved the design a little, and also got the price down a little.
I present to you: The 16-channel Servo Shield.
This shield is compatible with all the other servo controllers based on PCA9685 chip, but fits snuggly onto the D1 Mini. Angled headers for the servo let you stack them with other shields, or stack up to 64 servo shields, if you need to control a thousand servos for some reason. This shield uses I2C on pins D1 and D2, so it's incompatible with the RGB shield and the Relay shield, which use those pins for other things.
This project is completely open-source, and all the designs are available under a Creative Commons license. Details in the project's page on hackaday.io. I would absolutely love for this project to be picked up by the hobby electronics manufacturers around the world and sold even cheaper than I am able to make it.