Helper script to list all different fonts used in a specific Photoshop document. Do note that the PSD needs to be saved somewhere, a .csv file will be generated in the same folder listing all the font variants.

listFonts.jsx

var nicer_obj = function (obj) {
    var new_obj = {}
    for (key in obj) {
        if (obj.hasOwnProperty(key)) {
            try { new_obj[key] = obj[key]; } catch (err) {}
        }
    }
    return new_obj;
}

var seenIt = {};
var progress = false;
function recurseLayers(docRef, nufile) {
  var activeLayer;
  if (docRef.layers && docRef.layers.length) {
    for (var i = docRef.layers.length-1 ; i >=0 ; i--) {
      // Set the active layer to the next layer in the loop.
      if (progress) {
        activeDocument.activeLayer = docRef.layers[i];
      }
      activeLayer = docRef.layers[i];
      try {
        if (activeLayer.kind == LayerKind.TEXT &&
          activeLayer.textItem &&
          activeLayer.textItem.contents &&
          activeLayer.textItem.font) {
          if (app &&
            app.fonts &&
            app.fonts[activeLayer.textItem.font] &&
            app.fonts[activeLayer.textItem.font].name &&
            !seenIt[app.fonts[activeLayer.textItem.font].name]) {
            seenIt[app.fonts[activeLayer.textItem.font].name] = true;
            nufile.write( app.fonts[activeLayer.textItem.font].name +"," + app.fonts[activeLayer.textItem.font].postScriptName + "\n");
          }
        }
      }
      catch (e) {

      }
      if (activeLayer.layers) {
        recurseLayers(activeLayer, nufile);
      }
    }
  }
}

if (documents.length > 0) {
  progress = confirm("Would you like to see the active layer being inspected? (increases runtime significantly)");
  var fileName = prompt("Please specify a filename (.csv will be appended).", '') || activeDocument.name + " - Fonts Used";
  // Tell Photoshop not to display any dialogs.
  //displayDialogs = DialogModes.NO;
  // Create a reference to the active document.
  var docRef = activeDocument;
  CurrentFolder = activeDocument.path;
  // Loop through the layers one at a time. docRef.layers.length contains the number of
  // layers including the background.
  //Create the Excel comma delimited file in the current folder
  var nufile = new File(CurrentFolder + "/" + fileName + '.csv' );
  nufile.open("w");
  nufile.write("Font Name,Font Post Script Name" + "\n");
  recurseLayers(docRef, nufile);
  //Close the Excel comma delimited file
  nufile.close();
  alert("Finished, stored in: " + CurrentFolder + "/" + fileName + ".csv");
}
else {
  // Gives this message if you don't have a document open in Photoshop.
  alert("You must have at least one open document to run this script! ");
}
// Set the objects to nothing to release to the system.
docRef = null;