Meet the SparkFun ESP8266 Thing: a development board with a WiFi-enabled microcontroller that can be programmed to monitor sensors, automate appliances, and control lights. As we have covered it here in the past, these boards can be used to build internet-controlled flamethrowers and other exciting gadgets.
The ESP8266 is easy to use. You can develop firmware for it in Arduino. It features 802.11 b/g/n wireless connectivity. These boards are pretty cheap too!