The following boards are still experimental - some may never actually get completed.
EXPERIMENTAL INTERFACES
I2C connector - hardware-supported I2C bus adapter
Proximity Plug - 8-input capacitive touch sensor, I2C
SOIC Breakout Plug - pads to connect to SOIC packages
Voltage Plug - up to 4 DAC converters with 12-bit resolution, I2C
ABANDONED
Display Plug - 2-digit 7-segment LED display, I2C