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
Banana Pi - BerryClip 6led add-on DIY board
Banana Pi - GPIO extend board
Banana Pi - I2C GPIO extend board
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.
The Raspberry Pi GPIO Triple Expansion Board converts the single GPIO headers on your Raspberry Pi into three parts. DFR0385
A/C and C/A converter module for Raspberry Pi3, Raspberry Pi2, Raspberry Pi+ and Raspberry Pi minicomputers (MCP3021, MCP4716).
Relay output module for Raspberry Pi3, Pi2, Pi+, Pi minicomputers.
Real-time clock module (RTC - M41T00S) for Raspberry Pi3, Pi2, Pi+ and Pi minicomputers.
High performance full NFC compliant expansion board compatible with Raspberry Pi. EXPLORE-NFC