tedster - 8:27 pm on Dec 24, 2011 (gmt 0)
My preference for an HTML sitemap is to create it mostly for the user - and therefor to link it visibly from a "utility links" area somewhere in the template for every page. Now that xml sitemaps have become standard, I don't think it's important (or even good) to link to every URL in the site. Rather, I like to show the main structure in some sort of visual way - almost like a hot-linked wireframe.
This gives the visitor a visual sense of how the site is organized that can be quite informative in a way that the main navigation may not be able to do. It can even show a different organization - a differently "faceted" way of organizing the information architecture - for instance, content by application rather than content by product name.
An html sitemap of this nature also has an SEO purpose, in that it gives search engines another signal as to what the priorities of the various pages are - another reason not to link to every page. And yes, I do like to include a short phrase or sentence to clarify where each link goes. Often I like linked anchor text rather than displaying the actual URL.