Roughly two weeks after releasing iOS 5 Beta 4, Apple just unleashed iOS 5 Beta 5 minutes ago.
According to Apple, in order to install iOS 5 beta 5 over-the-air, you will first have to backup your device through iCloud. Then delete everything on your device by going to Settings > General > Reset > Erase All Content and then Settings. Finally, start the over-the-air update by going to Settings > General > Software Update.