A Server Object Extension to add open data format output to ArcGIS Server 10.1 and 10.2
Full dataset: http://localhost/arcgis/rest/services/SampleWorldCities/MapServer/exts/GeoJSONServer/GeoJSON?layer=0&f=geojson
Attribute filter: http://localhost/arcgis/rest/services/SampleWorldCities/MapServer/exts/GeoJSONServer/GeoJSON?query=CITY_NAME%3D%27Baltimore%27&layer=0&f=geojson
The above URL will query layer 0 of the SampleWorldCities map service for the city name "Baltimore" and return a GeoJSON feature collection containing this record.
Bounding box filter: http://localhost/arcgis/rest/services/SampleWorldCities/MapServer/exts/GeoJSONServer/GeoJSON?layer=0&bbox=-79,35,-75,40&f=geojson
The above URL will query layer 0 of the SampleWorldCities map service for features intersecting the defined bounding box and return a GeoJSON feature collection.
Bounding box filters - You can supply a bounding box parameter to filter results (GeoJSON only). This parameter generally follows the convention established by the ArcGIS Server REST API Export Map function, with a key difference. Like that function, you will supply a parameter called "bbox" with a set of comma-separated values xmin,ymin,xmax,ymax. The key difference is that these values must currently be decimal degrees and the extension will assume WGS84 for the spatial reference.