One of the first companies to focus on Wi-Fi was the AsyncLabs, who proposed a famous WiFi shield, including the appropriate libraries. What we propose is a new solution for Wi-Fi: this is a shield that the hardware was inspired by that of AsyncLabs, but in addition, we have provided a slot for microSD memory.
The basic component of the shield that we have made is a Wi-Fi module MRF24WB0MA manufactured by Microchip. The device is a Wi-Fi IEEE 802.11 RF transceiver, with a data rate between 1 and 2 Mbps, and with an internal antenna.
The WiFi shield supports both types of wireless networks infrastructure (BSS) and ad-hoc (IBSS) and is also allowed to connect to secure networks (cryptographers and are supported 64 and 128-bit WEP, WPA/WPA2 and TKIP, AES and PSK).
The library is constantly evolving, so we have provided a space where they will be published on http://code.google.com/p/wifi-shield-oe/ various versions available. http://www.open-electronics.org/arduino-wifi-shield/
Arduino WiFi Shield - [Link]