Quite by accident, I discovered that if you hold down the apple key and then "click and hold" on a blank spot on an IE page, you can grab and move web pages as if they were PDF documents. This makes for a much easier time of scrolling sideways as well as up and down.
[Editor's note: This isn't new to Jaguar or even OS X, apparently ... still, I don't think it's been mentioned here before. Thanks to Jensen G. for the clarifying email.]
Mac OS X Hints