There are rumors flying left and right about Apple releasing the iOS 4.0.2 firmware for iPhones and iPod touches and iOS 3.2.2 for iPad in only a few hours from now. This update will patch the PDF exploit which is used by JailbreaMe to jailbreak all iOS devices. If you accidently update to iOS 4.0.2 / iOS 3.2.2, it will be impossible for you to jailbreak and unlock straight away until a new tool is available. The only way you can jailbreak again will be by downgrading back to iOS 4.0.1 or iOS 4 for which you will need your SHSH blobs.
A little birdie told me ios update due in a few hours (better to believe than ignore) so go ahead and save your SHSH before it’s too late!
If you are on iPhone 3GS, iPhone 3G, iPod touch 2G/3G or iPad user, follow the complete step by step guide posted here to save your SHSH blobs using TinyUmbrella. iPhone 4 users can follow the guide posted here to backup their SHSH files.