Light sensor modules KY-018 and LM393 (3 and 4 pin) for a Raspberry PI...
Read the light values, use it to do things!
Electronic components are useful!
It's very useful
LED modules for Raspberry PI, Arduino
Everything you need to know about LEDs to get started.
Infrared Sensor HC-SR501 PIR Motion Sensor for a Raspberry PI and Arduino
How to use PIR sensor with your Raspberry PI.
Humidity and Temperature sensor DHT-11 (&DHT-22) for Raspberry Pi and Arduino
How to hook up the temperature sensor
Diodes for beginners
Not just LEDs
Relay Module KY-19 (Songle SRD-05VDC-SL-C)
Switch things on and off! Simple, cheap and functional.
Raspberry PI sensors
Sensors for RPI - overview
Resistors for beginners
Everything you need to know about the resistors
Sonar HC-SR04 ultrasonic ranger for a Raspberry PI & Arduino
How to connect HC-SR04 Sonar module to Raspberry Pi