You can use the Curse client to automatically find and install them. The top infobar and the buff bars addons are fantastic, but my favorites would be the gear manager and the deck manager ones so you can save abilities and gear sets individually and easily switch between them without having to worry about re-equipping gear or whatnot. Also, I got one that makes crafting not a pain-in-the-ass. And one that tells me when all my friends sign on or off. Fun!