These files can be used to style up the Open Street Map layers hosted on a Geoserver. I made these using the CSS extension for Geoserver. I attempeted to get the styles (colors, widths, etc) as close to the original OSM data as possible. However, at this time it is not an exact match. It is still a work in progress. Feel free to adjust the scale thresholds to suit your needs.
The styles area also used for the large scale, 1:10m Natural Earth data set.
Note: A new branch has been added with changes to the map. The [osm2] (https://github.com/melbsurfer/osm-geoserver-styles/blob/osm2/README.md) branch has the latest version of the styles.