Sprite sheet packer is a program that you download that lets you drag-n-drop images into the program that you can generate into a sprite sheet at the click of a button. It has several output format options and after you generate a sprite sheet, it also generates a text file that lists the dimensions and positions of each image in the sprite sheet. This tool will come in handy if you want to create sprites out of your smilies and other graphic images you use in your site.