The ESP8266 module I got looks just like an HC-05 Bluetooth module and works about the same way with AT commands over serial. There's not much documentation out on it yet, but there's a community starting to develop around it.
I built a little proof-of-concept demo around it. The demo is a web site hosted on google app engine that allows you to control the brightness of an LED connected to an Arduino. The Arduino polls the web site via the WiFi module and updates the brightness of the LED as you change the slider on the webpage. More documentation to come, but here's a quick gif of the ESP8266 demo in action