Review on Arduino Pro Mini 328 16MHz by Tyler Parker

I would definitely recommend getting one that has four extra inputs. Not all applications need (or want) them, but I like having so much hardware available and found a way to solder them in so everything is available. My recommendation: Solder the long sides of the pins under the sides ("down" in reference to the product depiction in the title picture). Solder the programming connector either straight up or with the pins at a 90 degree angle. The extra pins don't line up with anything else. So if you want to put it on a breadboard, pay attention to how the pins on the "auxiliary inputs" line up.