Open source
Emoncms – https://emoncms.org/3
GRAFANA – http://grafana.org/4
NODERED – http://nodered.org/3
Other
ADAFRUIT – https://io.adafruit.com3
BLYNK – http://www.blynk.cc/8
DWEET – http://dweet.io/3
EVOTHINGS – https://evothings.com/3
FREEBOARD – http://freeboard.io/10
GROVESTREAMS – https://grovestreams.com/3
KAA – http://www.kaaproject.org/overview/
PUSHBULLET – https://www.pushbullet.com/1
PHANT – http://phant.io/3
PROWL – https://www.prowlapp.com/faq.php2
REEKOH – http://reekoh.com/1
RESIN – https://resin.io/2
SENSORCLOUD – http://sensorcloud.com/2
THINGSPEAK – https://thingspeak.com/5
TWILIO – https://www.twilio.com/1
XIVELY – https://xively.com/1