A HighRanking's thread named Site Map Depth Question goes over the basics of building out a large site map. As you can see from the thread, you want to have less then a hundred links on a page. Anything more, may be pushing the spiders further then they want to go. So what do you do?
You can create a multi-page sitemap. For example, if you want to have a site map of states and cities, you would first list out the states and if you click on a state you would then see the cities within that state.
If you want to be fancy, you can go with Ralph's idea by using some form of + sign system to collapse the deeper pages under the higher level pages. So users can browse your site map in a windows navigator like method. But what about the 100+ link issue? I would make the top level links crawlable, and the others, not crawlable. Then allow the user and the spider to click on the top level links, and continue the same approach there. So this really is a mix breed between the idea above and the idea mentioned by Ralph. (will repost in forum)
Forum discussion at HighRankings Forum.