What are the best DIY Arduino Data Logger tutorials on the web?

As many in the forum already know, I've been working on an underwater data logger project for a couple of years now, and things are going pretty well. In the process I have come across plenty of other great Arduino based data logger projects, and after a while I got the feeling that some of us (myself included) were re-inventing wheel, often because we did not know about the work others had already done.

Recently, I discovered a social media site called list.ly, and thought I would try an experiment to see if the great data logger projects could be compiled together, with lots of people adding links to the projects they know about:

My hope is that the collective eyes and brains availiable in a forum as large as the playground could build a resource that is dramatically better than I could come up with on my own.

So if you know of any good DIY data logger projects that are on not that list, please post them here or directly to the list.ly thing (which I am still learning, so bear with me if it goes a bit slow)

I am specifically looking for projects that help others to build their own equipment, although a few commercial ones like the Adafruit logging shield will go in there too, because they also help so many people with their great tutorials.

Also take a moment to throw your up/down votes into the pot, as that's kind of the whole point of the list.ly idea.