Whew. Your subject header made it sound as if you were thinking about mapping the same content five different ways-- which would infuriate the user. (Or, at least, this user ;))
So you're thinking about five non-overlapping sub-maps so users don't have to plow past the four-fifths of the site that doesn't interest them? I don't see a problem, as long as there's a clear "back to top" option for users who say "Oh, wait, wasn't there something about widgets in this site?" Or links to "widget map", "gizmo map", "foobar map" et cetera, whatever is most convenient.
And you did say html sitemap, meaning the map for users. No relation to the xml sitemap that you may or may not produce for search engines' benefit.
I have a real estate website and I am also wondering how to get the sitemap to include all the mls house listings in the sitemap. This would be for the search engines to index the pages , any suggestions are welcome new to this.
If you are talking about a sitemap for visitors, that's exactly the way I do it for one quite large site about a far ranging topic. Not only do I believe that it's better for site visitors, but also makes it easier for me to keep track of.
webmaster tools now has a section for microformats , I think if you have a large amount of pages or products, google is asking you to break it down with schema data, not sure if you need more than 1 sitemap but I do believe google wants us to use the microformats within the sitemap.