ThingSpeak - Open source data platform for the Internet of Things. ThingSpeak Features
dweet.io - Ridiculously simple data sharing for the Internet of Things.
The IoT Guru - the IoT cloud backend company
Xively - Xively offers an Internet of Things product relationship management solution for enterprises.
IoTPlotter - IoTPlotter.com is a service which collects data from your IoT devices for long-term graph plotting and storage. It's completely free and made for the maker community.
AskSensors - The easiest IoT platform