According to an article on the Macworld website, iOS 5 has a couple features that are available but not enabled: 1) a panoramic photo feature and 2) an alternate way of invoking spelling suggestions. Interestingly, you can enable these features without jailbreaking your device. But you do have to tweak it a bit — so this is probably only of interest to the techies among you. Also, the features are pretty fritzy, which is possibly why they weren't enabled. Still, they give an indication of features we may see in the future.
The article says that to enable them, you need to use a free utility to edit the backup file for your device. Then you restore your device from the backup, and voila, you have new features. The article explains the risks and tells you how to make and save a pristine backup before doing this so that you can restore your device to its state before you fiddled with it. And it actually recommends against enabling these features.
The panoramic photo feature lets you pan a scene to create a 360-degree image. The text entry feature puts spelling suggestons in a row above the keyboard rather than in a bubble below the word. Tapping one of the suggestions selects the word. Macworld speculates that the panoramic feature will likely make it into a future iteration of iOS 5. It sounds like a great feature to have, though already available through third-party apps such as 360 Panorama.