Simply fire up your iDevice of choice and point the Safari browser to http://www.jailbreakme.com/ and click the Free button in the bottom left. Watch in amazement as the Cydia store is installed granting access to those apps deemed unworthy or distasteful to your iOS overlords.
Once completed, you can finally do all those dastardly ‘hacker’ things Apple fears so much, such as remapping your buttons, changing the font, or rotating your iPhone’s Springboard. The Horror!
Enjoy it while you can, early adopters! iOS 5 is just around the corner!