So, to be able to jailbreak in the future using the same tools (i.e. on iOS 4.2 and newer), you have to save your SHSH blobs. You can follow those 3 steps to save your SHSH blobs of any iOS device.Step 1: Download the latest version of TinyUmbrella (Windows, Mac, Linux), and make sure you're running iTunes 10 on your PC or Mac.Step 2: Launch TinyUmbrella and connect your iOS device to your PC / Mac. Now select ‘Advanced Option’. Your ECID number should already be there, and make sure ‘Location’ is set to ‘Cydia’Step 3: Now just click on ‘Save My SHSH’ and wait a few seconds
Well done, now you got your SHSH blobs saved.
[Source: Save SHSH Blobs of iOS 4.1 on iPhone, iPod touch and iPad]
NOTE: If you have problem in getting out from your "Recovery Mode", you can use Tiny Umbrella and select the "Kick Device Out of Recovery"