Apple released iOS 5 Beta 3 earlier today, and as usual when a new build is available, we are tracking down every cool new feature. I just found out about this new one while playing around the Settings app for my iPad.
If you go to Settings > General > Sounds and select "Text Tone," for example, you will be offered many more tones to choose from. I'm not 100% sure how many of these tones are new. but it seems to me that iOS 5 Beta 3 gives us access to 20 more tones...