While the BBC micro:bit is primarily aimed at schools, its low price (about $16) and ease of use makes it a great tool for learning and prototyping on.
The micro:bit is powered by a 32-bit ARM Cortex processor and comes with a built-in accelerometer, magnetometer and Bluetooth.
A unique feature of the micro:bit is the integrated 5x5 LED matrix that offers 25 individually programmable red LEDs to use as a basic display or output.
At $9, C.H.I.P. is a perfect demonstration of how cheap computing has become. You get what would only a few years ago have been desktop power on a tiny board.
OK, OK, I know that technically the Zero W is a member of the Raspberry Pi family, but this one is too awesome to not list!
Why?
Because for only $10 it offers a very impressive feature set:
The Omega 2 from Onion Corporation comes with built-in Wi-Fi (802.11 b/g/n) and on-board flash storage - all for $5!
The board runs a custom Linux distro that's based on OpenWrt but you can also choose to run FreeBSD.
The modular nature of the Omega 2 means that you can easily add features such as Bluetooth or GPS to suit your needs.
A coin-sized Linux computer that is totally open-source, and costs $20. This is a small, low-cost, totally open-source (both the hardware and software) computer that's ideal for projects such as IoT or building your own custom router.
A cheap, $23 quad-core powered board that's ideally suited for hobbyists.