Node-RED

http://nodered.org/

A visual tool for wiring the Internet of Things

Postscapes

http://postscapes.com/

Tracking the Internet of Things

openHAB

http://www.openhab.org/

“A vendor and technology agnostic open source automation software for your home.”

Contiki: The Open Source Operating System for the Internet of Things

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

Contiki: The Open Source Operating System for the Internet of Things

The Open Source OS for the Internet of Things

Spark

https://www.spark.io/

Spark gives you the tools to connect everyday electronics to the internet over Wi-Fi.