Multiple contact sheets from multiple folders

I'm sorry to say that it may not be possible, but saying that IF you are using a Windows machine you could  write your own contact sheet routine. BUT once again Adobe has screwed that up, but it can be rectified by downloading the Photoshop Option Plug-ins for CS5 Adobe - Photoshop : For Windows : Photoshop CS5 Optional Plugins

You would need to install the "Picture Package (ContactSheetII)" plugin then delete the contactsheetII.jsx from the application/presets/scripts folder. once this is done you can script a contactsheet.

You also have Picture Package back!

As an example.

createContactSheet(Folder("~").openDlg("*.*",true));

//addTitle("Mr So and So");
function createContactSheet(selectedFiles) { 
      var cSheetOpts = new ContactSheetOptions;          
        cSheetOpts.acrossFirst    = true; 
        cSheetOpts.bestFit        = false; 
        cSheetOpts.caption       = true; 
        cSheetOpts.flatten      = false; 
        cSheetOpts.resolution    = 300; 
        cSheetOpts.rowCount       = 2;         
        cSheetOpts.columnCount    = 3;          
        cSheetOpts.font         = GalleryFontType.HELVETICA; 
        cSheetOpts.fontSize      = 12; 
        cSheetOpts.height         = 3508/(cSheetOpts.resolution/72); //A4
        cSheetOpts.width         = 2480/(cSheetOpts.resolution/72);
        cSheetOpts.useAutoSpacing = true; 
        cSheetOpts.vertical       = 15;          // 0..1000 
        cSheetOpts.horizontal     = 1;          // 0..1000 
        cSheetOpts.mode = NewDocumentMode.RGB;  
      app.makeContactSheet(selectedFiles,cSheetOpts); 
} 
function addTitle(Title){
var Black = new SolidColor();     
Black.rgb.hexValue = '000000';
var newTextLayer = activeDocument.artLayers.add(); 
newTextLayer.kind = LayerKind.TEXT; 
newTextLayer.textItem.kind = TextType.POINTTEXT 
newTextLayer.textItem.color = Black; 
newTextLayer.textItem.font = "ArialMT"; 
newTextLayer.textItem.fauxBold=true;
newTextLayer.textItem.size = 22; 
newTextLayer.textItem.contents = Title; 
newTextLayer.textItem.underline=UnderlineType.UNDERLINERIGHT;
newTextLayer.textItem.justification = Justification.CENTER; 
newTextLayer.textItem.position = [ new UnitValue ( activeDocument.width.as('px') /2, 'px' ),  new UnitValue (newTextLayer.textItem.size*2, 'px' )]; 
activeDocument.flatten(); 
}