ThingSpeak - Open source data platform for the Internet of Things. ThingSpeak Features
The IoT Guru - the IoT cloud backend company
openHAB - "empowering the smart home" - vendor and technology agnostic open source home automation
dweet.io - Ridiculously simple data sharing for the Internet of Things.
AskSensors - The easiest IoT platform
Corlysis - Corlysis is a platform that helps you with storing and visualizing your time-series data.