UPDATE 2: How to install iOS 6 Beta on your iOS device – Link
Almost every other iDevice user is dying to get their hands on the first beta version of the newly announced Operating System, the iOS 5. Unless you have signed up for a $99 per year Apple developer program, you would need to wait until fall of this year to get your hands on the public release.
But you can always try the other way here:
1) Log In into Apple Developer Center and open iOS Dev Center page.
2) Select iOS SDK Beta Tab
3) Download and Install Xcode and iOS SDK 5 Beta.
4) Download and Install iTunes 10.5 Beta.
5) Download iOS 5 beta for your iOS Device (iPhone, Ipad, etc).
6) Connect your device to your Mac computer.
7) Make sure to backup your connected device in iTunes 10.5 beta.
8) In Apple Developer iOS Provisioning Portal, register your devices with UDID if you have not done so. This is how to get your UDID or search app store for UDID apps.
9) iOS 5 Beta file is .dmg archive therefore you need to open it in order to see .ispw, so click on it to run it.
10) Open XCode –> Under Windows Select Organizer
11) CLick on your device and then click on Software Version, In a drop down you will see Others or iOS 5 Beta (It may differ), then find appropriate iOS file which you prepared in step 9. If you do not see any other option for software selection, you need to get your iDevice into Development Mode first.
I hope the steps above were easy enough for all you iDevice owners to install the iOS 5. Get ready to experience new features including Notification Center, iMessage, Newsstand, Reminders, Twitter, Camera, Photos, Safari, PC Free, and many more features.