Do you already have an Arduino with an Ethernet Shield? Connect some sensors and send the data to ThingSpeak with this simple Arduino Sketch.
Once the data is collected by ThingSpeak, we have a number of ThingSpeak Apps that let you do something with it. Use ThingTweet to update Twitter if your Christmas Tree needs watered. Use React and TalkBack to control your thermostat. Use TweetControl to control a global network of lights!
[via ThingSpeak Tutorials]