I was reading through the quality guidelines and saw this:
"Offer a site map to your users with links that point to the important parts of your site. If the site map has an extremely large number of links, you may want to break the site map into multiple pages."
I submit sitemaps to Google for my sites but I don't usually have one on my site. I found this video (although it is a few years old) where Matt Cutts explains that having an html sitemap is not only good for users to find things on your site but also helps Google with crawling your site.
For those of you who use an html sitemap, do you use an online generator, or do you create one manually?