Raspberry Pi, but none of that is needed. Grab a 8GB+ SD Card, and follow along with this simple, easy tutorial:
On your Windows, Mac, or Linux PC, go to https://www.raspberrypi.org/downloads/noobs/ and download the NOOBS
Offline and network install zip file. It's about 1 GB in size, so this could take a bit. Go make a cup of coffee while you wait!
After downloading, extract the zip file to your new or freshly formatted (FAT32) sd card. Do not create a new folder.
Once finished, insert the sd card into your Raspberry Pi, connect power, HDMI video, (optional network cable) and keyboard/mouse and you are off and running. Just follow the Pi's onscreen install instructions.
Accessories we use and recommend are:
Logitech Wireless Keyboard / Mouse Combo
Edimax Wifi USB
2.5 amp USB Power supply
16GB SD Card