Android Things

https://developer.android.com/things/
https://developers.google.com/iot/

AliOS Things

https://www.alios.cn/things
https://github.com/alibaba/AliOS-Things

Huawei LiteOS

https://www.huawei.com/minisite/liteos/en/index.html
https://github.com/LiteOS

Raspbian

https://www.raspbian.org/

OpenWrt

https://openwrt.org/

Ostro

https://ostroproject.org/

Tizen

https://www.tizen.org/

uClinux

http://www.uclinux.org/

Yocto

https://www.yoctoproject.org/

Mynewt

https://mynewt.apache.org/

Mbed

https://www.mbed.com/

Contiki

http://www.contiki-os.org/

FreeRTOS

https://www.freertos.org/

Fuchsia

https://github.com/fuchsia-mirror

NuttX

http://nuttx.org/

RIOT

https://www.riot-os.org/

TinyOS

http://webs.cs.berkeley.edu/tos/

Zephyr

https://www.zephyrproject.org/

http://os.51cto.com/art/201611/521377.htm - 面向物联网的几大开源操作系统