One of the many new, under-publicized features of iPhone Software 2.0 is the ability to take a screenshot of whatever happens to be on the iPhone’s screen at the time. The process is simple: hold down the home button, and then quickly press the sleep/wake button on the top of the phone.
Once the buttons are released, the screen will flash white for a brief moment, letting you know the shot has been taken. The screenshot can then be found in the iPhone’s Camera Roll, and can be copied to a computer on the next sync, or emailed to a photo sharing service or to friends.
This same tip should also work on the iPod touch, providing it has been updated to software 2.0. Screenshots are created in PNG format, as opposed to the JPEGs made by the iPhone’s Camera application.