The Cricket One is a fantastic new board from Tony McKahan!
This board uses an ATMEGA328PB which is similar to the controller that is used in the Arduino Uno, Arduino Nano, and Arduino Lilypad. This version runs at 8MHz with the internal clock of the controller. You will need to use the 'Minicore' Board Manager set to 'ATMEGA328PB' and 'Internal 8MHz' for the Arduino IDE to communicate with it.
It has built in USB support with a USB Micro connector and a CH340C USB Interface.