If you're making a web page, it's almost inevitable these days that you're going to want to put some kind of graphics into it, if only a text effect or (shudder) a background texture. The GIMP coupled with the image utilities of the NETPBM package is an excellent choice--especially if you don't have access to Photoshop, or are determined to take the moral high ground and use only free software in the development of your project.