What is the best location for a sitemap?

I’ve been using the google sitemap generator plugin for a little while now but never really gave much consideration to where the location of that sitemap should be. As it is, most of my wordpress blogs are within a subdirectory on the domains they are installed in. This is where the plugin naturally looks for the xml and xml.gz files for it to write to sitemaps and where they are currently located on my server.

Is this really the best place for them to be? I’ve read a little bit on sitemaps.org that the sitemap should be in the root of the domain. Now I tried to move my sitemap files and use a custom path to the files but when I try to rebuild the sitemap it tells me it’s having a problem locating the files.