For people wanting to dabble in HDR beyond what Apple provides on iOS I'd suggest a look at HDR3 from developer Christopher Herbon. This US$0.99 app takes three different exposures in rapid succession, which are then combined to give you much more dynamic range. Bright areas of the photo won't be overexposed, dimmer parts won't be lost in shadow.
The app supports a full 8 megapixel resolution on newer iPhones, and has some built-in image stabilization. After the image is taken, there are adjustments available for saturation, temperature, gamma, sharpness, brightness and contrast. You can crop the image, and add from a selection of frames.