I hacked an example into the maptimes leaflet map to have multiple popups open concurrently. Here is a map of some Maptimes. Go to one of em and learn how to make this map better or make your own!
See: Maptime on Github
Modified http://cdn.leafletjs.com/leaflet-0.7.3/leaflet.js to a secure url
Modified http://maps.stamen.com/js/tile.stamen.js?v1.2.3 to a secure url