I have used the Asynclabs WiFi shield which i found to be excellent. Have a look whats available in the shop.

This design uses a MRF24WB0MA chip to handle the wiFi connection. You can download the library for the shield and the schematic  from here.  http://ruggedcircuits.com/html/yellowjacket.html Also the asynclabs is still having a website where you can find the software libraries and some examples.

This project is a simple web server displaying a single webpage using the asynclabs shield and an arduino. Here is an example of the same hardware collecting the weather from a server at LAX airport in Los Angeles USA and displaying it via the serial interface. The same can be done with local METAR data from many airports in the world.

 

WiFi shield links

http://nl.mouser.com/search/refine.aspx?Ntk=P_MarCom&Ntt=121032507   for 10 pcs costs 19.59 euro
http://theiopage.blogspot.nl/2011/10/connecting-mrf24wb0ma-to-arduino.html
http://code.google.com/p/wifi-shield-oe/
http://www.open-electronics.org/arduino-wifi-shield/
http://www.linkspritedirect.com/product_info.php?products_id=121 price 19.35 – 21.50