Click2Map allows you to organize your markers into fully customizable groups and subgroups to make working with large numbers of markers more efficient.
Groups have properties that can be defined individually: different groups can for example use a different default icon, which makes it easy to visually represent markers with common properties.
Groups can easily be shown/hidden to let you visualize only the markers you need on your map. Groups are also great for bulk operation - selecting all the markers within a group is very easy. Groups can be created within groups for an even finer organization of your markers.