[NOTE: Since this post was first published, Shape2Earth Version 1.0 has been released as Shareware.]
I spent part of the day looking to see what kind of free shapefiles are out there for use with my newly dubbed Shape2Earth open source GIS shapefile to KML converter. The simple answer is that there are "tons". I played around quite a bit trying to poke holes in Shape2Earth. Things seem pretty stable at this point, but I want to get it out to more people to see what breaks.
Below are a couple of quick maps I made with downloaded shapefiles.
Building footprints, Carrboro, North Carolina.
Average size of farms in Iowa by county .
Migration of Africanized Honey Bees in US by county.
Building footprints, Austin, Texas.