I think that the name "MenuSnippet" in that guide is just hypotethical (or maybe there has been a snippet of that name somewhere in the beginning, I don’t know really). But there is alot of snippets that can be used to do a menu. I personally think that Wayfinder
is the best snippet to date, but there is more and more excellent resources being made constantly. Snippets can be used in many ways though.. for example, you could use Wayfinder to do list of news on your site, or FAQ listing with script.aculo.us effects, etc..
Some other snippets that are suitable for menus: DropMenu, Ditto, ListChildOrSibs, ListSiteMap, ListRelated, etc.. see Resource repository