It's interesting that you mention custom mapmaking. Google provides a similar service - creating a KML file hosted from a Google Spreadsheet. Here is the newest version: http://www.google.com/earth/outreach/tutorials/spreadsheet.h...

I've recommended it to a non-technical family member (he's a realtor) and they were able to create and host their own kml-based maps within an hour's time. Note that it does not use polygon based building markers, but rather addresses (and coordinates), which are simpler for non-GIS people to use.