Here’s a list of 10 types of add-ons for the RasPi — with links to tutorials for incorporating them — from RaspberryPi-Spy.co.uk:

During my time with the Pi I’ve experimented with various devices and sensors. Here is my Top 10 list of devices to connect to the Raspberry Pi. In most cases they are very cheap and easy to interface and are great building blocks for more complicated future projects. I’ve included links to more detailed posts where I can and many of these include example Python scripts to help you get going.

From robot cars to security systems there are plenty of ways of combining these mini-projects into some amazing creations! If you need to buy a present for a Pi owner then these are good starting point.

• Ultrasonic Module
• PIR Movement Sensor
• Stepper Motor
• 16×2 or 20×4 Character LCD Display
• USB to Serial Module
• USB WiFi Dongle
• Mini LCD Screen
• BerryClip 6 LED Buzzer Board
• USB Bluetooth Dongle
• Nintendo Wii Controller

Read more.