The Arduino Nano is a small, complete, and breadboard-friendly board based on the ATmega328.
It has more or less the same functionality of the Arduino Uno, but in a different package. It lacks only a DC power jack, and works with a Mini-B USB cable instead of a standard one. It includes an ch314a USB to Serial chip so only needs a USB cable (supplied) in order to program it.
Cable not Included.