After the success of my Arduino Uno I2C Master board, I started thinking that I could improve the board. Well ... make it more extensible for one thing, and allow me to use the board for other stuff as well. I figured if I could break out the pinouts of the ATMEGA328P-PU, that I could have a board that I could use for more than just the I2C Master, but that I could use for that purpose too. Also, I could add and ICSP header to the board so that I would have less juggling of chips and boards.
That became my goal for another breakout board/Arduino Uno self-build.