Jim's Edit: If you already installed the release candidate listed in the tip below and want to use the final release of iOS 5, use the Restore button while your iOS device is plugged into iTunes. That will make iTunes install the latest version of iOS 5. Make sure you back up your device.
Since iOS 5 has been released, there is no need to use the files linked to below. The tip below was written before the final release. Plug your iOS device into iTunes now and you can get the final release version of iOS 5 instead of the prerelease linked to below.
iPad, iPhone and iPod Touch users are salivating about the upcoming release of iOS 5. But why wait for the final release when you can get the release candidate right now!
1. Make sure you backup your iOS 4 install. Upgrading to iOS 5 will wipe your device.
2. Download the iOS 5 software. The various versions are listed below.
3. Download the iTunes 10 Beta 7 and install it.
4. Plug your device into iTunes and go to the settings page for your device. Find the restore button and hold down Option on Mac or Shift on PC and click Restore. When asked for the software you want to install, go to the folder where you put the iOS software you downloaded and then select the IPSW file.
5. Your device will turn off and the install will complete.
6. Follow iOS 5's setup and you can restore your iTunes backup.
That's it! Now you have iOS 5 running before it's officially released. Enjoy!
How to Upgrade to iOS 5 Right Now | Lockergnome
Now read: Get your iPhone ready for iOS 5