Shapefile to geojson & topojson based on Natural Earth data - http://www.naturalearthdata.com/
GeoJSON courtesy of - http://www.mediafire.com/?5faef9y5ct8mn
I converted above GeoJSON to TopoJSON using The Distillery - http://shancarter.github.io/distillery/
Drill down each folder for the GeoJSON and TopoJSON files (check out folder structure readme file).
New to Github so any suggestions are welcome.