Here’s a little known feature of the iPhone 2.0 upgrade, available for 1st gen iphones and included with the new 3G iPhone. To take a screen shot of whatever is on the screen, hold down the sleep button on the top of the phone and then depress the home button. A screen shot will be taken and saved in your camera roll. From there you can email it to yourself or someone else.
Here’s an example I took of my favorite (and most used application) on my iPhone, iNozbe.