Here are a list of the most popular addons that people will be running day 1.
LootDrop - This shows what you have looted in a small preview window at the bottom right of the screen
Pawkette's Scrolling Battle Text - Shows scrolling text during combat of dammage done and taken.
Multi-Quest Tracker - Keep track of all of your ongoing quests at once!
ZrMiniMap - Shows a minimap in the upper
right corner of the screen.
What addon's will you be using for launch?