The OpenStreetMaps is a popular tile source used by many online geographic mapping specifications. You can read more about it at http://openstreetmaps.org/ and details about the tile set at http://wiki.openstreetmap.org/wiki/Slippy_map_tilenames#Zoom_levels
OpenSeadragon has added support for OpenStreetMaps as a tile source thanks to Rainer Simon (http://github.com/rsimon).
Inline configuration couldn't be much simpler for using OpenStreetMaps as a tile source.
Configuration is done via the 'tileSources' option ( or programatically ). Because of its rich levels and depth, we slow down the zoomPerScroll option a litte, wrap horitonally, and hide the navigator. Also we set a lower minimum zoom image ratio to allow the user to pull back just a little further.
OpenSeadragon({ ... showNavigator: false, wrapHorizontal: true, zoomPerScroll: 1.2, minZoomImageRatio: 0.5, tileSources: [{ type: 'openstreetmaps' }] ... });