If you are one of die-hard Apple fan then you must have saved the SHSH blobs before upgrading the iOS using TinyUmbrella or iSHSHit which subsequently used to downgrade your iDevice firmware to an older version. Today, NotCom, Developer of TinyUmbrella has been upgraded to support iOS 5.0.1. However, currently there is no procedure available to downgrade an iPhone 4S as Apple has changed the way its signs firmware. The newly released version has been updated to TinyUmbrella 5.01.00.
Even though there is still no working solution for restoring 5.x on iPhone 4S I have released a 5.01.00 so you can at least save 5.0.1 SHSH. I have added tentative support for at least saving 5.0.1 SHSHs for iPhone 4S but as of now we are unable to use them fully.
However, if you want to downgrade from iOS 5 Beta and have your SHSH blobs avaiable for iOS 4 then follow the step-by-step guide to downgrade your iPhone, iPad or iPod Touch using TinyUmbrella 5.00.10
You can also jailbreak iPhone, iPad or iPod touch on iOS 4.3.5 using RedSnow, iOS 4.3.3 using Redsn0w, JailbreakMe or to Jailbreak while preserving your baseband (software unlock) see TinyUmbrella, SnowBreeze & PwnageTool.