I was made aware today of a great site called Web Design Practices developed by Heidi Adkisson. As she explains:

Surprisingly, I found very little research documenting the frequency of seemingly common (perhaps even standard) design practices such as the left-hand navigation bar, blue underlined links, and top-of-the-page global navigation. I was surprised because as a consultant working with clients, every project seemed to bump up against strongly held beliefs about what was "standard" on the web. I had my suspicions, but no data, that solutions being put forth as standard were common but by no means employed by all (or nearly all) sites. I wondered: Are de facto standards on the web myth or reality? I decided to investigate.

Her site contains simple statistics on the interface practices of popular websites with almost no comments or suggestions. It's up to the designer to interpret her numbers and decide how they'll affect decisions. A very helpful and informative site I'll be keeping my eye on. She has also written an article at Boxes and Arrows on the subject.