public interface IMapPane 

public static IEnumerable<IMapPane> GetMapPanes()
{
  //Sorted by Map Uri
  return ProApp.Panes.OfType<IMapPane>().OrderBy((mp) => mp.MapView.Map.URI ?? mp.MapView.Map.Name);
}

public static IReadOnlyList<Map> GetMapsFromMapPanes()
{
  //Gets the unique list of Maps from all the MapPanes.
  //Note: The list of maps retrieved from the MapPanes
  //maybe less than the total number of Maps in the project.
  //It depends on what maps the user has actually opened.
  var mapPanes = ProApp.Panes.OfType<IMapPane>()
              .GroupBy((mp) => mp.MapView.Map.URI).Select(grp => grp.FirstOrDefault());
  List<Map> uniqueMaps = new List<Map>();
  foreach (var pane in mapPanes)
    uniqueMaps.Add(pane.MapView.Map);
  return uniqueMaps;
}

// find a mapview by its Caption using the FrameworkApplication Panes collection
var mapPaneCaption = "USNationalParks";
var mapViewPane = FrameworkApplication.Panes.OfType<IMapPane>().FirstOrDefault((p) => p.Caption == mapPaneCaption);
if (mapViewPane != null)
{
  // activate the MapPane
  (mapViewPane as Pane).Activate();
  var mapView = mapViewPane.MapView;
  if (mapView != null)
  {
    // get the layers selected in the map's TOC
    var selectedLayers = mapView.GetSelectedLayers();
  }
}