HTML sitemap is not only good for users but for Search Engines too as it comprises of links to the posts which helps in distributing pagerank to all the posts. In addition with XML sitemap HTML sitemap is indeed important. HTML sitemap should be composed of the links to the all the posts or at least the important posts and categories of a blog, as this will help search engine bots to efficiently reach and index the pages of your blog. To know more watch the following video by Matt Cutts: