As pointed out by Dago, I personally use a Fon (La Fonera) or Meraki router (with OpenWRT) for connecting Wifi to a serial connection.
http://www.dd-wrt.com/wiki/index.php/LaFonera_Hardware_Serial-Cable-Porthttp://www.geocities.jp/arduino_diecimila/wifi/a2p_ddwrt_en.html