Here is some grist for the mill that may be useful.......
My projects feed data to to the Internet using Xively. I have W5100 ethernet shields and feed by cable to my router in the normal manner. This was fine for test purposes, but it is not practical for proper operations here as the installation needs to be on the other side of the house.
My original intention was to then communicate via bluetooth, with a second Arduino feeding to the router, but the Bluetooth is not up to the job, even though it is fine for local data collection. I have some NRF24s but I have never used them and I don't expect themn to be that much better than Bluetooth. I haven't been too keen on getting a wifi shield, they seem to be troublesome and are certainly expensive.
I am now using a WiFi repeater.
http://www.ebay.com.au/itm/350786460622?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
I believe this device is a Baiyuyi but goes under at least one other name - Satechi. It is an elegant package but spoilt by a crude AC plug adapter. This is of no concern to our transpacific cousins as that adapter is not needed. The device is essentially a wireless router with four exclusive modes. I am using it as a repeater, with Arduino connected by the short cable provided.
The manual isn't bad but the pictures in the ad are a helpful addition. I did have to have two goes at setting the repeater up for my network, first with a laptop and then with the desktop, but that might have been me.
Once set up, the device works perfectly. No additional additional hardware or software is required for the Arduino - just take it out to the laundry and plug'n'play in the way Bill Gates can only dream about.
It is an obvious solution for me as I already had a working setup with an ethernet shield but even an all-new combination of ethernet shield plus this repeater would be less than half the price of a wifi shield and it brings a lot other benefits to the table as well. In my case it actually saved the cost of a second Arduino. I can't recommend it highly enough.