One quick note about the SHSH thing. It only really applies to the iPhone 3GS and above (iPhone 4 and all iPads). It wasn't until this generation that Apple made hardware changes to prevent the device from restoring without their seal of approval. The 3G started requiring Apple's approval starting in iOS 4, but it's only a software thing and can be bypassed using some jailbreak tools (I think it involves making a custom firmware file but I don't know for certain). Older iPhones I believe can be restored to any firmware supported by the device.
