I'm working on a GIS web app where a user can draw a polygon on a map (a Microsoft map) to define a region. The vertices are placed by right clicking on the map placing vertices at each click and when the user right clicks the first vertex it completes the polygon. After that a user can right click an edge to add a vertex on that edge. At any time, a user can left click to drag the existing vertices around the map. My only remaining hurdle is a way to allow the user to remove vertices from the polygon in a way that makes sense.
In our map application, we don't use info boxes or other map pop ups anywhere else, so doing so here seems a little uncharacteristic for the webapp as a whole. All of our controls are in dialogs that are free floating and not attached to locations on the maps.