This is a post from another forum by Bentley Skeie from H&H Color Lab:
Here is a series of videos that I recorded.
By the time you watch the last video, you should be able to select a folder of images, run the action that I show you how to create, to place a logo on all of the images.
It does take into account if the image is horizontal or vertical for the placement.
Video 1
Here is a series of movies that I did that show how to take your logo and create a custom shape from that log.
YouTube - Photoshop - Custom shapes tutorial (Part 1 of 4)
Video 2
Then how to use the custom shape with layer styles to apply the logo to your images.
YouTube - Photoshop Using Custom Shapes in Layers (Part 2 of 4)
Video 3
Then automating that with an action.
YouTube - Photoshop - Watermarking Using Shapes with Actions (Part 3 of 4)
Video 4
And finally, how to create a script to run the action to place the custom shape and layer style on your images (both horizontal and vertical) and prepare them to upload as web sized images.
YouTube - Photoshop - Automate It All w/ Scripts & Actions (Part 4 of 4)