What is an Arduino, and why do I want one?

Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software. It's intended for artists, designers, hobbyists, and anyone interested in creating interactive objects or environments.

I guess that includes me.

Home computers are great at communicating with other computers and (sometimes) with us, but they have no idea what is going on in the world around them. The Arduino is a way to take computer programming into the physical world

In theory, one of these could monitor the current flowing between two nails in the soil of a potted plant. When the soil gets dry, the current drops and the Arduino sends a signal to open a valve which would water the plant.

In a sense it reminds me of my first computer, an Apple II, where 30 years ago I spent over $1,000 and still needed to connect it to a tape recorder and an old TV to make it at all useful.

The Arduino Uno is the latest revision of the basic Arduino USB board. It connects to a computer with a USB cable and contains everything else needed to program and use the board. By itself it costs $30, or $27from Amazon. However, to move this project into my comfort zone, I will probably buy the SparkFun Inventor's Kit for Arduino (which costs $95 plus shipping; or get the Arduino Professional Kit from Amazon which is exactly the same thing, but costs $90 and eligible for free shipping). The kit is nice because it includes lots of the bits needed to build a dozen basic circuits.  Plus, not that I'm afraid of soldering, these projects all have no soldering required. 

All in all, this should be cheap fun and a little educational.

Update:  Change of plans. Ordered the SparkFun Inventor's Kit for Arduino with Retail Case. It cost more, but this version includes a plastic carrying case to organize all the components (see the video at the link). Keeping all these small parts organized seems worth the extra bucks.