Although twitter can be used for disseminating everything between mindless gossip to useful news, it also makes an interesting conduit for remotely controlling an Arduino. How? Using a very simple sketch you can have an Internet-connected Arduino board use the twitter search engine to look for a particular hashtag (e.g. #arduino). Upon returning a result the Arduino can then take action. This is exactly what Gregory Fenton has done, however for his example when someone mentions a certain hashtag, his electronic sweets dispenser is activated - thus handing out a treat.
When putting together your next Internet-enabled Arduino project - save time, space and money with the Freetronics EtherTen. Apart from being fully Arduino Uno-compatible, it has onboard Ethernet, microSD socket, full USB interface (so you don't need a costly FTDI cable just to upload a sketch!) and supports optional Power-over-Ethernet.