I saw a couple of videos from a group who have reviewed upcoming Apple products in the past. It looks as if it has a new feature where you can run multiple apps in the background and open/close them quickly and efficiently. It also had a new folder system. I'll search around to try and find the videos for you. Overall it looked okay but honestly i was expecting something a bit more exciting! (bearing in mind this is NOT an official video from Apple; more to come, hopefully )
iOS 5 Leaked on White iPhone 4 ? - Here i dug around for a bit and found the link enjoy!!
By the way, this isn't the iPhone 5 case/design etc. this is a video of the iPhone 5's operating system iOS 5 running on a (white) iPhone 4 and again, this is a Vietnamese group, NOT an official Apple vid.