Apr 6th 2010 6:04PM I'm not sure if this has been mentioned, but for smaller screens I've found it really useful to ditch the unit frames completely and get an HUD (IceHUD is my preference, but there are heaps [MetaHUD, DHUD2, etc]) coupled with Grid/Vuhdo for party/raid frames. They aren't to everyones liking but I find I save a ton of real estate, and it helps keep my UI clean. As a tank I also find it more useful having that information readily available in the center of my screen.
Also, as others have mentioned, a huge thumbs up for Opie. I used to be chronic for having EVERYTHING on bars (to the point where I had 6 action bars all full on my Druid :S) until I saw the light, and now I struggle to fill 2 action bars (and even then I've got still some unnecessary abilities on there). Keeping visible buttons to abilities you only regularly use in combat can get rid of an amazing amount of clutter.