Easiest. iOS. Jailbreak. Ever.
Using your iDevice, just download Cydia from http://www.jailbreakme.com/ and you're ready to go! I've even found Apps (Yes, Apps that are NOT available in the App Store!) that allow you to use your computer to connect to your iDevice and look at the hidden internal stuff! To get MobileTerminal, DO NOT GET IT FROM Cydia because it is an old version that does not work with iOS3-4!!! Instead, follow instructions in this video: http://www.youtube.com/watch?v=oZNAUpp_RcI ! Hurry! It's only legal to Jailbreak until the end of 2011, unless the exemption is renewed!
This has been typed on a Jailbroken iPod Touch (Don't worry. All iDevices are supported, but Apple is working on a patch.) that has MobileTerminal on it!