Simon Willison, an English web wizard blogger (who, btw, was just hired by Yahoo) has written a greasemonkey extension to dynamically change and drastically improve the navigation of the Library of Congress's digital library, the American Memory project.
For those of you unfamiliar with Greasemonkey, it's an extension to Firefox that lets you do this sort of thing: display a website how YOU want it, not how the developer programmed it.
One of the comments suggests that Simon should contact the website and ask them to incorporate design changes into the site. There's something unlikely to happen! But it does point out another truism of the developing web culture: expect your information to be reused in ways you didn't imagine, by some.
On the other hand, UI guru Jakob Nielsen just pointed out that most users use the default choices, so you need to make the defaults work well. Most users won't use greasemonkey to fix your site. They'll just go away.