In this link you find 50 interesting boards from 2015.
Top boards are Arduino Zero, Arduino Wi-Fi Shield 101, Adafruit METRO 328, Tessel 2, Arduino GEMMA or less known as Adafruit Bluefruit LE Micro, pico-Platinchen, Piccolino or Neutrino.
On this website you find too development boards for SAM microcontrollers, boards with accelerometers by Atmel or very interesting type of Arduino - SDuino.

Check this website
http://blog.atmel.com/2015/12/16/rewind-50-of-the-best-boards-from-2015/