As I was looking for such a method, I stumbled upon a great Firefox add-in from Chris Pedericks called the Web Developer Toolbar (download). As the name implies, the free toolbar is intended to help Web designers test their pages, but it can also be used to show only the text of Web pages, which often makes them easier to read--and to print out.
In addition to making the pages easier to print, the text-only versions are also much easier to scan for specific information. (Note that you can retain much of the page's original formatting--minus images--by keeping CSS enabled.)
Tomorrow: Put Microsoft Word's styles to good use.