Raspberry Pi 2 Quad-Core 900 MHz 1GB RAM – Model B

The Raspberry Pi 2 Model B is a serviceable credit card-sized single-board computer which costs around $35.

One can can get everything needed (if you happen to have a spare keyboard, mouse, and monitor) to set up a system for about $70.00.

Raspberry Pi 2 Complete Starter Kit — Includes Raspberry Pi 2 900 MHz Quad-Core CPU (1GB) — Edimax EW-7811Un Wi-Fi Adapter–20 Page User Guide–Clear Case–Power Supply–Kingston 8GB Micro SD Card and Micro SD to SD Adapter–HDMI Cable and Heatsink