If you have a 3G-capable PocketPC phone with Wifi you need check out WMWifiRouter. I just tried it and its awesome!
WMWifiRouter is a tool to use your Windows Mobile 6 (possibly 5) as a WiFi < -> GPRS/UMTS/HSPA router. It’ll allow you to use WiFi capable devices to connect to the internet through your phone’s data connection.
More info at: