ThingSpeak - Open source data platform for the Internet of Things. ThingSpeak Features
FHEM - FHEM (TM) is a GPL'd perl server for house automation.
The IoT Guru - the IoT cloud backend company
Conrad Connect - Service for managing smart home devices
AskSensors - The easiest IoT platform
Homebridge.io - Homebridge is a lightweight NodeJS server you can run on your network that emulates the iOS HomeKit...