Recently, Tom MacWright announced geojson.io, an app for "drawing, changing, and sharing GeoJSON-formatted map data." My colleague Eric Kansa has used it to map finds at Poggio Civitate: http://geojson.io/#6176329. It's cool to see GeoJSON finally catching on in the archaeology/history/humanities circles where it has some roots. Wednesday, GitHub announced that GeoJSON Gists now get the same maps as GeoJSON files in repositories.
The GitHub announcement was bigger news, but I'm more interested in geojson.io. I'd love to see the interface reused in Pleiades somehow, someday.