Darn cool, Matt.
So cool, in fact, that there's a risk people will try to turn on all of the maps at once (or just too many for their computer to handle).
You can use GE to fix this pretty easily by looking at the properties of a folder and selecting "show contents as options".
The relevant KML is explained here:
http://earth.google.com/kml/kml_tags_21.html#listItemType
Basically, you add a ListStyle to whatever styles you have already and give it a listItemType of radioFolder:
Code:
<Style id="radioFolderExample">
<ListStyle>
<listItemType>radioFolder</listItemType>
</ListStyle>
</Style>