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.
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.
BeagleBone Black is a low-cost, community-supported development platform for developers and hobbyists. This $55 board allows you to boot Linux in under 10 seconds and get started on development in less than 5 minutes.
A $135 quad-core board that's just as at home running Android as it is Linux.
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.
A $40 Arduino that's idea for integration into a commercial or industrial product.
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.
Banana Pi M3 is a super charged single board computer with an Octa-core processor and 2GB of RAM. It also features Gigabit Ethernet, 2 USB, SATA, WiFi, Bluetooth, and HDMI connection. It can run on a variety of operating systems including Android, Lubuntu, Ubuntu, Debian, and Raspbian.
The easiest way to create internet-connected devices - no programming, soldering or wiring required. IFTTT support allows it to connect with any web service, like Facebook, Gmail and Twitter, or hardware like NEST and Philips HUE.
All for just $59.95.
The Parallella computer is a high performance, credit card sized computer based on the Epiphany multi-core chips from Adapteva. Starting at $99, the Parallella can be used as a standalone computer, an embedded device or as a component in a scaled out parallel server cluster.
The NanoPC-T3 is the bigger brother of the NanoPi 2 Fire, and features an octa-core processor which has enough power for commercial and industrial applications.
A cheap, $23 quad-core powered board that's ideally suited for hobbyists.
At around $92, the Intel name doesn't come cheap, but this Arduino-compatible board is turning out to be a popular choice.
The PixelPro features a i.MX6Q Quad-core ARM Cortex-A9 running at 1.0 GHz, with 2D and 3D GPUs and an embedded 2GB 64-bit DDR3 RAM, which means that it is capable of running rich multimedia applications, embedded web servers, digital entertainment systems, industrial control systems, and high definition video.
At $129.95, the PixelPro is not cheap, but you get a lt of power for the cash.