By usin Cydia Make my life easier, thanks button you can quickly save your iPhone 3Gs, iPhone 4, iPad and iPod Touch 3G SHSH blobs. In this tutorial I will be guiding you how you can use TinyUmbrella to save iOS 4.X+ SHSH blobs.
Click on Save SHSH and if you wish you can change location of file by going under advanced tab.
Within Seconds your SHSH blobs would be saved. If you have a jailbroken iPhone with 4.x+ iOS, make sure you do this step ASAP. As iOS 4.2 is coming soon for everyone. You can check under logs to find if your SHSH blobs was saved in cydia or not.