Note: Some of the listed leveling addons provide overlapping or incomptible functionality. Make sure to pay attention to which you install so you don’t have unnecessary addons.
Carbonite Quest
Carbonite Quest HUD Interface
Carbonite Quest Map Interface
Carbonite Quest provides a complete quest database for leveling in WotLK. It gives you an improved quest list, a directional arrow showing you the fastest route to your next objective, and an extremely powerful world map that makes questing much easier. You can record favorites to keep track of locations, targets, and general notes.
Clicking on an objective on the quest display interface immediately gives you coordinates, distance, and direction to your next quest location or turn-in. You won’t need to constantly tab out of the game to your browser to look up quest information anymore, it is all built-in to Carbonite Quest. With this addon you’ll be leveling in WotLK faster than ever before.
LightHeaded
Lightheaded Addon
LightHeaded is a simple addon that displays the comment text from WowHead along-side your quest log. No more tabbing in and out of WotLK to read through the Wowhead comments. Now it is all conveniently in game! LightHeaded works directly with TomTom to provide coordinate direction tracking.
QuestHelper
QuestHelper is very similar to Carbonite Quest. It automatically sorts your quests based on waypoints related to the quest, and displays the order to do them to minimize travel time. On your world map you will see green waypoints noting which quest objective to complete next, and yellow waypoints showing other objectives on your list. If you have TomTom installed, QuestTracker will automatically use it to display your next waypoint direction and distance.
TomTom
TomTom is a very simple addon that allows you to add waypoint to your world map, in Northrend, or any other continent. It also gives you an arrow showing you the distance and direction
GetToThePoint
GetToThePoint can automatically turn in quests, accept quest, and skip gossip text, when possible. It removes a few of the tedious steps necessary in questing in WotLK, letting helping your leveling go just a little faster.
DoubleWide
DoubleWide is a very basic addons that double the width of the WotLK quest log. It makes reading quest text and viewing all of the quests in your log much easier.
AutoMaton
Automaton offers all of the functionality of the other automation addons, and much more. The main options that are going to help you with leveling are: automatically repairing when you are at a vendor who can, selling of grey items, and skipping of gossip text. Automaton does much, much more however, so if you aren’t interested in all of its functions, you might prefer one of the more specialized addons.
Auto Ding
Auto Ding will help you annoy your friends and guildmates by automatically announcing each time you level! You know you’re going to do it anyway, save yourself the typing. 
AutoProfitX
AutoProfitX automatically sells grey and white items when you go to a vendor. Now you won’t have to hunt through your bags searching for [Severed Talon] ever again.