R to GeoJSON
UPDATE As you can see in Patrick’s comment below you can convert to GeoJSON format files with rgdal as an alternative to calling the Ogre web API described below. See here for example code for converting to GeoJSON with rgdal. GitHub recently introduced the ability to render GeoJSON files on their site as maps here, and recently introduced here support for TopoJSON, an extension of GeoJSON can be up to 80% smaller than GeoJSON, support for other file extensions (.topojson and .json), and you can embed the maps on other sites (so awesome). The underlying maps used on GitHub are Openstreet Maps. ...