FWIW, I added XML site maps to the community directories.
The maps are neither pretty, nor are they useful for humans. The maps are supposed to be useful by search engines. This is an example. This is the Index to the site maps.
The only useful information that the maps contain is an update time stamp. It took me a whole day of programming to figure out how to get the correct information into that timestamp.
The main advantage of the sitemap protocol is for dynamic web sites where the data changes randomly on a regular basis.
It will be interesting to see if the maps have any positive effects on visitors to the site.
BTW, the directory structure has had over 4 million hits. There's about 17,000 listings in the directory. That is about 235 hits per listing. When I put the directories together. The totals are lower than I was hoping to see.