When I am done with my Photoshop concept I add guidelines where I want the image to be sliced. At the bottom of the Photoshop toolbar there is an icon that will switch you over to ImageReady. ImageReady will automatically make slices from where your guidelines are and you can optimize them individually. It will also export the html and css for you, no tables, no gaps and it even puts the sliced images in to an image folder for you.
