I always like trying things out that promise to change the way I browse, but for some reason or another I could not get Tab Effect to get up and running via my Firefox installation. It looks like the folks over at CyberNet did though.
If you are just the slightest bit familiar with Linux then I am sure that you have heard of XGL. It is what adds all of the realistic 3D effects to the windows that you drag around and the virtual desktops that you switch between. Of course, one of the most popular features is probably the 3D cube for switching between your virtual desktops.
Looks like some kinks may still need to be worked out, but this would be a neat feature to see in a future version of Firefox. Not sure if it helps with productivity, but a little eye candy never hurt anybody.