Taking a screenshot on your iPhone is really useful for documenting stuff or when submitting a bug report to a developer (a picture is worth a thousand words!). I mentioned how to do this in an Aside a few months ago, but I really think it deserves a little more attention. It's so useful, but also so simple:
Step 1: Press and hold the Home button
Step 2: Press and release the sleep/power button
The screen will flash white for a second and return to normal. Now you can find the screenshot in the Photos section and email, or send it to MobileMe.
