Owning a wifi-only Ipad means that it's a constant adventure for me to explore new ways of going online when I'm not at home. One method that I've been successful with is to install and use this nifty free beta software from Connectify (www.connectify.me) .
Basically, what it does is to convert your wi-fi capable desktop/laptop into a wireless access point. So if you happen to be on a business trip in a hotel that only has an ethernet access point in your room, you can tap that internet connection for your Ipad (or even your Iphone in order to save on expensive 3G data roaming charges).