Well, what do you want to do? If you haven't done anything before, making a blowhole or increasing the size of your existing intake/exhausts is a good way to start. If you want the case to be somewhat mobile, installing a handle or two is a nice addition. Adding a window to a case is also another easy mod. If you have the most basic of electronic skills, adding neon or ccfl is easy, or if that's a little too much try changing the current red and green LED's you have in the case right now.