We really wanted to minimize the cost of an Arduino. The Arduino Pro Mini is like the Arduino Mini (same pin out) but to keep a low cost, we used all SMD components, made it two layer, etc. This board connects directly to the FTDI Basic Breakout board and supports auto-reset. The Arduino Pro Mini also works with the FTDI cable, but the FTDI cable does not bring out the DTR pin so the auto-reset feature will not work.
The latest and greatest version of this board breaks out the ADC6 and ADC7 pins as well as adds footprints for optional I2C pull-up resistors!