TinyUmbrella!

redsn0w is a utility that will jailbreak your iPhone or iPod Touch, allowing it to run apps that are not approved by Apple.

iSHSHit allows you to backup your SHSH blobs from Apple directly on your iDevice for later downgrading.

iFaith is a program that can save the SHSH blobs of the current version of iOS that's running on your jailbroken iPhone. It will work any version of iOS, whether or not that version is still signed by Apple. Saving your SHSH blobs allows you to restore your device to the saved version of iOS at anytime, even when Apple has stopped approving restores to that version.

PkgBackup is a backup application for jailbroken iPhones that backs up & restores all of your Cydia apps, your Cydia sources, and even your homescreen layout. Simply sync your backup with iTunes or Dropbox- then, when you update or restore your device, bring back all of your Cydia apps by redownloading PkgBackup afterwards.