Apple has released iOS 5 beta 3. If you are a registered Apple developer, you can download it from the Developer member Center.
The installation process is exactly the same as for previous beta releases:
A more detailed step-by-step guide to installing iOS 5 beta is available.
Remember, the iOS version needs to match the version of iTunes, otherwise you won't be able to sync/backup. For those who have lost track of which version is which, the table below will help you match your version of iOS to iTunes.
Let me know how you go and what new functions you discover in iOS 5 beta 3.