From Evan Schoenberg:
Reading Glasses turns your iPhone 3Gs into a pair of spectacles, able to zoom from 2x to 8x on anything you can (or cant) see. Bring small print or minute details into focus.
Designed for one or two handed operation, you can use the standard pinch-and-zoom technique or thumb the vertical slider along the side of the screen.
Tap the Pause button to freeze the image.
Use your finger to move around; uniquely, Reading Glasses lets you view the full image captured by your iPhone 3Gs even when zoomed in, making it much easier to read a line of text at high magnification.
Never find yourself unable to read tiny print - on a pill bottle, in a menu, in a newspaper article, or on the back of a box - because you forgot your reading glasses again!
* Note: Reading Glasses requires an iPhone 3Gs (for the autofocusing lens) running iPhone 3.1 or later. Be sure to bring the text or object into view a moment so the lens has a chance to autofocus! *