iPlus is a *fully automatic* tool for setting up your iPhone! For Windows and Mac OS X (intel/PPC)
It will downgrade the bootloader, unlock, jailbreak and activate the iPhone. And even better, it will also install the most important and common packages as well as several fixes, with a custom payload for installing other packages.
Bootloader downgrading uses BL 3.9FakeBlank, so it is fully reversible.
AEP-Emu (DE/EN)
DMG Page (DE)
Indie Retro News (EN)
Retroguru (EN)