A Narrow View
Here is a site that I think shows some real intelligence. (In the formatting, not necessarily in the content!) I offer it to the Tablet community as an example to learn from. When you've got it open, maximize the window then switch between Portrait and Landscape and watch what happens.
8/30 update: As so often happens to me,* the day after I posted this I found one site that does seem to make a serious, and mostly successful, effort to address this. The Student Tablet PC web site does indeed shift into narrower and wider display versions based on screen orientation. Kudos to Tracy, Trevor and Andrew. I say only mostly successful because wide links in the page can't break and still force horizontal scrolling, but it isn't required to read the text of the page itself. That and the artifacts on the left and right all fit within the display area of the page. Very nice!
*The surest way for me to find something I've been looking for or to remember something I've been trying to recall is to ask my wife. As soon as the words are out of my mouth, I find the thing.