Waves effect

You need a graphics card that supports Quartz Extreme to get the wave effect in Dashboard (or the fade-transition when cycling desktop backgrounds) though I suspect that if you install X-Code, and have a look in /Developer/Applications/Performance Tools/Quartz Debug and go to the Tools menu, you might be able to turn on Quartz 2D Extreme. Be warned, though, if it works it'll mean your graphics card will be trying to do things it wasn't designed to do - you might get crashes, slowdowns, weird graphic effects and so on.