I wrote about the ability in the new Mac OS X to drive portrait-mode displays. Normally, on Powerbooks, this only applies to external displays. There is, however, a hidden way to rotate the internal display, which can be nice if you want to view a whole page:
Open System Preferences (it mustn’t already be running) and hold down Alt while clicking the Displays icon. You’ll then get the option to rotate the display.
Warning! This doesn’t rotate the trackpad! It can therefore be a fun challenge to manipulate the cursor after doing this. If you have a mouse, you can turn either it or the laptop through 90 degrees and everything is easy! This works quite well: