This site has a nice list of free Photoshop plugins you can use to spiff up your sites.  People often argue that site design or looks don't matter as long as it has good products or information available -- this argument is bogus, and is a crutch for the lazy and incompetent webmasters all around the world. 

Design and looks are absolutely essential to the success of your site, and you should treat it as such.  Your site design gives a first impression just as you do when you meet someone for the first time.  There is nothing else to judge you or your site on at first except looks -- take the time and use the tools at your disposal to make it look great.