This is the only tricky part.
This step is the key to getting the whole ladder of monkeys to work properly -- combine solettes in series with a superglued shingling technique. Each solette, or any chunk of mono or polycrystalline PV silicon for that matter, outputs around 0.5 - 0.6VDC, which is not enough voltage to do very many useful things. So, we need to combine enough of these solettes together in series so that their voltage outputs add up.
In order to power an arduino (3.3V - 5V, depending on the arduino model), we will need a minimum of 7 solettes in series (or, 3.5Vopen). The solettes we are using output Im (or, the max current at the maximum power point of the cells - about max power point here: http://en.wikipedia.org/wiki/Maximum_power_point_tracking) of around 100 mA per solette. So, since we are combining the solettes in series, the voltages add up, but the current does not. Or, to put it another way, 7 of our solettes in series will output 3.5VDC-ish and 100mA with a perfect load outside in the glorious noonday sun.
If however your solar panel is jammed into a lightbulb, like a 14W compact fluorescent, you can deliver about 10mA (if demanded).
Back to the solettes: The (+) output is the grey underbelly of the first solette in your shingled fan-stack. The (-) output of the series connected fan can be accessed either at the bus bar or white silver ink runners on the blue top surface of the final solette in your stack, or by using a "false" solette that doesn't produce electricity but just serves to bring do the top surface connections to a solette underbelly. Watch the video here for more explanation: http://www.youtube.com/watch?v=nsX6r-_Nn6Y
What to do:
A few dabs of superglue (again, the very thin clear liquid stuff -- also known as cyanoacrylate), a few seconds of pressure, and you've got yourself a solar series connection! Repeat 7 times for an Arduino Pro (or, 8 times if you are using a false solette to pulldown the power to your copper tape), or 10-11 times for most other Arduinos. This also works with the new Leonardo boards.