Users

Libaries:

• OpenLayers
• OGR (http://gdal.org/ogr/drv_geojson.html)
• MapFish Java implementation? https://trac.mapfish.org/trac/mapfish/ticket/73
• GeoJSON Python Library, http://pypi.python.org/pypi/GeoJSON/1.0a3
• Shapely (GeoJSON Geometries)

Servers:

• FeatureServer
• GeoServer
• WPServer
• MapBender
• Pleiades?
• Knowhere? I Think.

Desktop Apps:

• FME
• Cadcorp SIS (I hear? can't find a link)
• Arc2Earth, according to http://tinyurl.com/2oo5o8

Web Services:

• geo:truc, http://www.geotruc.net/
• FireEagle, I hear?