Thingspeak -nevermind how easy to set up- has a few hurdles that I ran into and that, judging from reactions, other people are struggling with as well.
Things you need:
W5100 EthernetShield (if you have the old ENC28J60 ethercard, look here)
Sensors (such as DHT11 and BMP180)
You will find a better program to start from right here: