If you don’t mind killing your iPhone’s ability to connect to a mobile carrier, you can upgrade to iOS 5 Beta without an Apple Developer account.
Through a backdoor hack associated with the new setup process in the iOS 5 activation screen, you can install the developer preview. This WILL lock you out of connecting to a carrier.
We will reiterate Gizmodo’s warning:
Warning: While this operation should be simple, we are not responsible for what you do to your iPhone. Once completed, you will not be able to connect to a carrier. Proceed at your own risk.
Gizmodo has the details:
1. Download the iOS 5 IPSW file from the web (it’s easy and readily available. Just Google it and torrent it down).
2. Update your iPhone using iTunes. To do this, connect your iPhone to your computer, click on the Check for Update button with theOption (Mac) or Shift (PC) key pressed. Select the iOS 5 IPSW file from the place you downloaded it to.
3. Wait until it upgrades. A new activation screen will appear.
Activate iOS 5
1. Triple click the home button. This will activate the Voice Over.
2. Triple click the home button and Emergency Call will appear.
3. Click on Emergency Call and, while it’s switching, swipe with your three fingers down.
4. The Notification Center will appear!
5. Click on the Weather widget. The Weather app will load.
6. Click on the home button to exit to the iPhone’s springboard.
I suppose the main use for this hack would be to update a non-3G iOS device such as an iPod Touch or Wi-Fi iPad. Don’t be a fool and do this to an iPhone or 3G iPad.