Atmel ATmega32U4 microcontroller comes preloaded with an Arduino-compatible bootloader, and the board includes dual motor drivers that can deliver 1.7 A per channel to two brushed DC motors. Pololu 3119
The core of a small robot, either as an auxiliary controller atop a Raspberry Pi base or as a complete control solution on its own. Its Atmel ATmega32U4 microcontroller comes preloaded with an Arduino-compatible bootloader. This version does not include any through-hole components or connectors, allowing for customized assembly or standalone use. Pololu 3118
Raspberry Pi Expansion Board, Supports Arduino XBee. Waveshare ARPI600
Expansion Shield X300 with RTC real time clock; audio input and output; USB hub; Bluletooth, WIFI; SATA interface. Compatible with Raspberry Pi Model B+, Pi 2 Model B and Pi 3 Model B
A highly cost-effective audio hat which fits on the GPIO of the Raspberry Pi B+/2B/3B, uses i2S interface audio solution, supports 24-bit /192KHz high quality sound, compatible with other audio equipment via RCA lotus socket, includes a built-in high fidelity headphone amplifier, where you can plug in a 3.5mm audio jack directly. DFR0449
Highly cost-effective multimedia hat compatible with the Raspberry Pi Model B+/2B/3B. Decodes and separates voices from HDMI signal, completely solving the poor quality problem with Raspberry Pi integrated sound card. DFR0450
GertDuino is an Arduino and Arduino Uno compatible GPIO expansion board for use with the Raspberry Pi by Gert van Loo.
High performance full NFC compliant expansion board compatible with Raspberry Pi. EXPLORE-NFC
I/O Expansion board for Raspberry PI B+. PiFace Digital 2 add-on board for Raspberry Pi that allows for connecting things that will influence the world around it
PiFace Relay Motor Control Extra (Board) for Raspberry Pi
PiFace Relay Extra (Board) for Raspberry Pi
PiFace Relay Board for Raspberry Pi
Motor/power controller board for the Raspberry Pi
PiFace Control & Display is a plug and play device that allows you to use and control your Raspberry Pi without a keyboard, mouse and monitor.
Raspberry Pi Expansion/Evaluation Board, features various interfaces