It's now possible to add multiple kml-files to the map (version 2.12 and higher).

With the Google renderer, you'll need to set the center of the map yourself. 

{mosmap kml[0]='http://tech.reumer.net/images/florida.kml'|
kml[1]='http://tech.reumer.net/images/allservices.kml'|
centerlat='0'|centerlon='0'|zoom='1'|
kml[2]='http://tech.reumer.net/images/Countries.kml'}

!Warning! JavaScript must be enabled for proper operation.

With the GeoXML renderer, you don't need to set center. It will zoom automatically. Also you can sort the items inside a kml file in the sidebar (asc or desc)

{mosmap kml[0]='http://tech.reumer.net/images/florida.kml'|
kml[1]='http://tech.reumer.net/images/allservices.kml'|
centerlat='0'|centerlon='0'|zoom='1'|
kml[2]='http://tech.reumer.net/images/Countries.kml'|
kmlrenderer='geoxml'|kmlsidebar='left'|kmlsbwidth='200'|kmlsbsort='asc'} 

!Warning! JavaScript must be enabled for proper operation.