These are the libraries I use in my projects. Nothing special, just:
- flyingFishHelper - for moisture and rain sensors
- rgbLED - for common cathode RGB LEDs
- led - for normal LEDs
- ultrasonic.h - for ultrasonic sensors
- ky033.h - for those line-following sensors
- motor.h - to control DC motors
- TCS230 - for colour sensors (needs testing)
- flame - for flame/fire sensors
- PIR - for PIR motion sensors
It's easier to have them in one place when I want/need to change them.