Using the multitude of sensors and modules available for the Arduino platform you can capture all sorts of data and have the board make take action based on what has been measured. Furthermore you may want to capture or log this data with a PC - and one example of doing this has been explained quite well by Electronut in India. They have created a simple guide that shows how to export data in real time via the USB port and then capture it using python, and the plotting it in graphical form. Doing so "frees" the data in real time and gives you more options to take advantage of.
If you've heard about this "Arduino thing" - but not sure how to start - then the best way to learn is with our Experimenter's Kit for Arduino:
The package includes a wide variety of parts, sensors and modules including: a servo motor, lights, buttons, switches, sound, sensors, breadboard, wires and more. Furthermore a Freetronics Eleven Arduino-compatible board is included to make this an extensive hobby experimenter, inventor and starter kit. However we don't leave you alone to figure it all out, included is a great project and instruction booklet, plus access to a supporting web page and software examples. In other words - this is everything you need to get started for a fun range of electronics and Arduino related projects!
So to get started or for more information and to order, check out the product page.