LIExposeController, our control of the week, was developed by LinkedIn for their iOS application, and offers up an Exposé-like navigation paradigm for iOS apps. You can check out an example of this in the wild in LinkedIn’s own iPhone app, of course. LIExposeController acts as a container view controller*, much like UINavigationController or UITabBarController. It manages a set of UIViewControllers as separate “stacks” so that users can easily switch between multiple screens. Apache 2.0 licensed.
* the control is still iOS 4-compatible, from my understanding.
Check out the source code, or see a demo of the control on YouTube first: