It’s good to see that more and more websites have a simple and usable sitemap (every good CMS should generate one by default).
Here’s what Nielsen has to say about those sitemaps:
One of the oldest hypertext usability principles is to offer a visual representation of the information space in order to help users understand where they can go.
I can only add: a well-thought-of site navigation + breadcrumb should try to give the visitor that same feeling.
People rarely use site maps. In Study 2, only 7% of users turned to the site map when asked to learn about a site’s structure. This is down from 27% of users in Study 1.
The good news is that users can actually find the site map in those few cases where they want to. In Study 2, 67% of the users successfully found the site map when we asked them to “Find a page that lists every part of the website.”
More facts an findings on Nielsen’s website.