HoloToy ($0.99) offers a surprisingly effective 3D experience on the iPhone and iPad. (Click here for iPad version.) According to the press release, it works by "distorting the 3D scenes displayed on screen in a way our brains would expect based on the current angle of the device, all in real time. It presents a believable 3D experience that appears to extend right into the device itself." The video gives you a good idea of what it looks like. It comes with a couple 3D games, with plans to add more, and other features.