The Raspberry Pi is a remarkably fun toy. Of course I use the word “toy” with a lot of reservation. It’s is one of those gadgets that comes along once in a generation that can single handedly spark the imagination of anyone who comes near it. Simply put, it is a complete working computer about the size of a deck of cards. Everything you need is right there, simply plug in a USB keyboard and mouse (I recommend a Logitech mouse+keyboard combo so that both use the same USB Unity Adapter), an HDMI capable monitor (most all are these days), a HDXC flash card with an operating system on it (the same kind of cards 99% of cameras use), plug in the power (it uses a micro-USB adapter for power) and you’re good to go.
I won’t go into the details of getting and setting up a Raspberry Pi because there are plenty of resources out there on the Internet to help you with that. A good place to start is the official website for the Raspberry Pi organization. http://www.raspberrypi.org. For purchasing a Raspberry Pi here in the United States I find Amazon has the best prices and lots of cool add ons for it. I recommend the “Model ‘B'” or “Model ‘B+'” over the “Model ‘A'” as the Model B and B+ have twice the RAM as the Model A. Also, if this will be your first Raspberry Pi then I recommend one of the “Kits” that will give you everything you need to start out including a case, an SDHC card with several operating systems to choose from, power adapter and, in some cases, a USB WiFi adapter.
