Thoughtful, detailed coverage of the Mac, iPhone, and iPad, plus the best-selling Take Control ebooks.
How to Make an iPhone Screenshot

Want to take a screenshot of something on your iPhone or iPod touch? Press the Home button and Power button briefly at the same time, and an image of your screen will be saved to the Photos app (and will sync with iPhoto when you next connect). Don't hold the buttons too long or your device will either power down or reboot.

From Angus Wong