Originate Labs has released PanoLab, billed as "an elegant, free* tool that enables photographers to assemble multi-frame panoramas directly on the iPhone."
Using photos taken on the fly and/or already on your iPhone, PanoLab stitches them together into a wide-screen vista that can then be saved/edited/shared like any other photo file. It can use as few as two — and as many as thirty — images to do this, and also "applies perspective correction and linear projection to make many
photos from one viewpoint align into a cohesive wide-angle view."
*The "free" applies to the basic PanoLab app. There's also a PanoLab Pro with more features — and a US$4.99 pricetag. One caveat: according to iTunes reviewers, neither basic nor Pro app offers a truly seamless stitching of images, so proceed accordingly.