ThingSpeak - Open source data platform for the Internet of Things. ThingSpeak Features
AskSensors - The easiest IoT platform
The IoT Guru - the IoT cloud backend company
Xively - Xively offers an Internet of Things product relationship management solution for enterprises.
dweet.io - Ridiculously simple data sharing for the Internet of Things.
DataGekko - IoT Telemetry platform ready for the next generation of internet connected devices.