Arduino shields are boards that can be plugged on top of the Arduino PCB extending its capabilities. Shields are easy to mount, and cheap to produce. These accessory hardware items allow you to control Arduino projects with your phone, with a blue tooth shield or even a touch screen to add a visual component. Within this section, there is a large database of shield makers to choose from, as well as, some examples of particularly interesting shields.
Here is the all inclusive Adafruit Data Logger Shield webpage. There is a downloadable PDF that gives step-by-step instructions on how to build a temperature and light data logging device. The PDF includes:
1. Soldering Sheild to Aruino 
2. Coding 
3. SD card set up 
4. Wiring up the shield 
5. Making graphs with data! 
This device is great for plotting data to be used in spreadsheets and analysis. The Real Time Clock (RTC) timestamps all your data with the current time, so that you know precisely what happened when.
It comes with:
