If you are wondering how to use your iPhone 3G as a modem to get super fast 3G internet connection on your laptop, then you have come to the right place. Here is a summary of how you can do that:

Jailbreak your iPhone 3G. Install two packages called 3Proxy and MobileTerminal that are available in the Cydia application that is installed when you Jailbreak your iPhone. Create an ad-hoc wifi connection on your laptop and lock you iPhone to the ad-hoc connection. Find out your iPhone IP Address and note it down. Start the SOCKS Server by running the MobileTerminal application and typing in "socks".

Quit the MobileTerminal application and start the safari browser on your iPhone. You iPhone will look for the ad-hoc WiFi connection but won't be able to use it. You can now switch to 3G data connection. Go to the proxy network settings on your Firefox browser and type in the iPhone's IP address and Port number 1080 in the Socks Server field.Load the firefox configuration file by typing about:config in the browser and change the value of network.proxy.socks_remote_dns parameter to true.

There you go, you are all done! Now start browsing the internet using the 3G internet connection. For details jump over to Into Mobile.