Hi everyone..
I need to connect my Arduino with internet in some cheap way,and someone tell me about the router tp-link wr703n with openwrt..I can buy it at only 21€ here http://www.dealextreme.com/p/tp-link-703n-ultra-mini-portable-3g-802-11b-g-n-150mbps-wifi-wireless-router-light-blue-white-102903 .And I can connect this via USB port.
That is a good alternative to wifi shield,I know, but before buy it I wanna ask you: do you know some other device/router more cheaper or more powerful(whithout high price)..otherwise I'll by this product.
Thank you all and sorry for my english 
An arduino, $20 ethernet shield, and a $40 netgear router can make a wireless setup like below.
thank you for ur response..but i'm searching something some solution under 30 €..for example my first solution cost 21€..I'm searching something more powerful or more cheaper..
What data do you want to pass over the wifi?
I ask this because some wifi APs/routers have TTL serial port and with opensource firmwares it is possible to access these ports from across the wifi. I don't think you could use it to run a web server or client but could allow you to pass data over wifi.
I did this with one of my cheap wireless IP cameras, I was able to break out the serial port and send data to it with the default firmware and a few commands from the manuals.
only 20-50 bytes/second..a web server is not essential..is also true that if is possible install the webserver,is better
Otherwise I'll write a c++ program with socket to interface with Arduino..