Open Source FPGA Dev Board In Small Form Factor

Great prototyping FPGA platform, which fits nicely into a breadboard, and can be easily embedded into any project of yours
iCEBreaker-Bitsy
The FPGA board iCEBreaker Bitsy is an open-source FPGA development board that is a compact version (36mm x 18mm size) of the iCEBreaker FPGA development board.
Available in a Teensy form factor, the iCEBreaker Bitsy is a great prototyping FPGA platform, which fits nicely into a breadboard, and can be easily embedded into any project of yours. 
The compatibility with the open-source FPGA design tools like Yosys, nextpnr, IceStorm, Icarus Verilog, SymbiFlow, nMigen and others makes the board easy to work with. This means the board is low cost and has a nice set of features to allow for the design of interesting projects. At the same time, the user can still choose to use the proprietary vendor tools.
Pinout diagram

Features & Specifications

128 Mbit (16 MB) quad SPI double data rate (QSPI-DDR) flash
64Mbit (8MB) quad SPI (QSPI) pseudo SRAM (PSRAM)
Lattice iCE40UP5k FPGA5280 logic cells (4-LUT + Carry + FF)
120 Kbit dual-port block RAM
1 Mbit (128 KByte) single-port RAM
PLL, 2 x SPI, 2 x I2C hard IPs
Two internal oscillators (10 kHz and 48 MHz) for simple designs
Eight DSP multiplier blocks for signal processing such as audio synthesis and software-defined radio
Low power consumption ideal for battery-powered applications
Three 24 mA drive and 3 x hard IP PWM (can drive RGB LEDs and small motors)

I/O options include

A current-controlled RGB LED (current settable in the FPGA, also contains PWM hard IP)
Two on-board indicator LEDs (one of the LEDs is shared with the PSRAM Chip Select line)
One pushbutton
USB-C connector capable of USB 1.x (Full Speed) operation. Fully controlled by the FPGA and available to your FPGA designs (Officially supported by the LUNA project)
24 GPIOs around the edge of the board, pinout compatible with the popular Teensy boards. Distance between pins is compatible with classic DIL IC sockets.

The FPGA board can host CPU soft-cores such as PicoRV32, PicoSoC, RISC-V and others that are programmable through a pre-loaded DFU bootloader (easy to use with dfu-util)
The product can be obtained from 1BitSquared.com. As of now, it seems to be sold out but will become soon available after the conclusion of the CrowdSupply campaign.