Adafruit IndustriesWi-Fi Shield | 1534Kit e schede di sviluppo RF/Wireless

From the Manufacturer: 

For years we've seen all sorts of microcontroller-friendly WiFi modules but none of them were really Adafruit-worthy. Either they were too slow, or too difficult to use, or required signing an NDA, or had limited functionality, or too expensive, or too large. So we shied away from creating or developing a WiFi Arduino shield. 

The CC3000 hits that sweet spot of usability and capability. It uses SPI for communication (not UART