I hate to bust your bubble on this, but I don't think you will find such a list, especially with the added criteria of white hat. It's really difficult to fully understand a website's entire optimization and strategy from an outside view. Plus, are we speaking of strictly site structure or all aspects of SEO? Wikipedia kills the SEO game by being so massive and having so many inbound links. Tough one to list off.
But if I had to suggest 5 sites to start with I believe that these sites would be great to study:
Zappos.com - Good site. They do a lot of SEO work on their website. I trust their team.
Logitech.com - A well built site. They try to follow all the white label stuff as well.
SEOmoz.org- Maybe it's a bit of a cop out, but the reason you are here is because they are recognized as an authority on the subject.
http://www.mattcutts.com/ < With the exception that you will want to navigate to his blog. But other than that, his site should follow all the white guidelines.
And per Avinash, http://lds.org does good SEO work. I've also run into them at a SEO conference or two.
Of course, all the above are well trafficked sites and very large. Matt's is probably the smallest of the group. If you are looking for smaller websites then I'd just refer to the search engine and who ranks well for any given term.