Helpful app: Paparazzi!
I'm doing some basic design/planning for a new section of the Filmmaker Magazine web site, and I needed a screenshot of the current home page. If you're on a Mac, you can hit just command-shift-4 -- if all you want is the a shot of the top of the page. But what if you want an image of the whole site, top to bottom? Paparazzi to the rescue. Enter the URL of the site, hit Capture, and you're done. Perfect for redesigns and mockups, and it's free.
Enjoy this extra white space due to the long image. Think deep thoughts.