WriteMaps is a web based tool that you helps you quickly draw a conceptual diagram of your website.
You may also use the tool to plan the layout of an upcoming site or for generating the sitemap of an existing website as in this example.
The tool has a very intuitive interface and the favorite feature is that you can share sitemaps online (each sitemap gets a unique URL) or you edit them with co-workers.
Now unlike your WordPress plugins that create sitemaps exclusively for search engines, the sitemap written inside Writemap is fit both for human and search engine consumption.
The downside is that this tool may not be fit for large websites as you have to create pages (nodes) manually.
Related: Fix XML Sitemap Issues in Blogger