Apple recently released iOS 5 beta and iTunes 10.5 beta. It is available only for Apple registered developers. But you can try it too. Remember that you do it at your own risk. Below you will find iOS 5 download links for iPhone 3GS, iPhone 4, iPod Touch 3G, iPod Touch 4G, iPad 1, iPad 2, Apple TV 2G and download links to iTunes 10.5 Mac and Windows.
Keep in mind that your iDevice will need to be activated, your UUID needs to be registered in Apple. Installing iOS beta on a non-activated device will render it useless. If you need help with registering UUID - write us, we will try to help..
Remember that currently there is no jailbreak for iOS 5 released. UPDATE: If you need a jailbreak - download it here.
iOS 5 will have hundreds of features. Here is one that wasn’t talked about too much, but it is an often requested feature - the iPhone 4 LED flash will now light up on incoming calls and alerts. Obviously, you can enable or disable this. This is a nice feature that was previously available only to jailbreakers.
Sn0wBreeze will also preserve baseband version if you need carrier unlock. If you have updated the baseband to version 06.15, you can use this tutorial to update to iOS 4.3.3. If you have iPhone 3GS and need to update baseband to 06.15, you can do it too (may disable your GPS).