How to build a basic Arduino data logger

Folks from our latest collaboration suggested that the Cave Pearl Project blog has grown into something of a spaghetti monster, and they asked me to produce a short one page summary of the most recent build instructions:

How to Build an Arduino Data Logger

I realize that many others have posted similar information to this forum, but one thing that makes our project a little different is that these plans are 'field tested' in significant numbers, and they are also used in my wifes Instrumentation courses. Generally she has them build the Uno/breadboard units right at the beginning of the course, so they can learn how to program, and then they assemble their final project around the promini style loggers.

Most of them have no previous experience with electronics, and the loggers themselves are not the point of the course, but simply support important lessons about sensor calibration and the complexities of environmental sampling. She reports that replacing the Campbell scientific data loggers that they used to use, with Arduinos has really improved student engagement.