This is much easier than I ever expected it to be. I’m not sure about previous versions, but I know this is possible in both Photoshop CS and CS2. First open any layered Photoshop file and hide a few layers.
Then, in the Layers Pallete, click on the little arrow in the upper right and select "Delete Hidden Layers."
That’s it! – very similar to the "Select Unused Items" in the Flash Library window, only better. It deletes them for you.
[Photoshop] Don’t drag all of your layers to the trash, hide the layers you want to delete and get rid of them all at once.



