These three add-ons can help clean up your UI by providing information where you need it.
Broken LFD (WoWInterface)
Hate the evil eye on your mini-map? Broken LFD provides a neat and tidy place on your favorite data broker to display what you’re waiting for while queuing. When scrolled over you can see how long you’ve been waiting as well. A nifty broker for any dungeon seeker!
My favorite functionality of ForteXorcist now in an easy to use, lightweight package. ncDebuffTimer shows every debuff that you cast on any target. Extremely useful for warlocks in particular, you can cast your dots on a limitless number of targets, and see the remaining time on your dots for each mob, whether you are targeting them, focusing on them, or not.
ToolTipTabs (WoWInterface, Curse)
People love to link… maybe your friend is trying help you find the best piece of gear, or you are comparing the axes of Littlefoot with those of Crusher–in either case, having tabs all over your screen can be annoying! ToolTipTabs allows you to having stacking tooltips with a simple tab interface to change between the multiple options. You can also drag out tabs if you so wish, providing just want you want on your screen.
ToolTipTabs also works with achievements, which can be a great help when trying to compare who has what in order to prioritize the dungeon for everyone!