WoW Horde Leveling Guides
Zygor's 1-80 Alliance & Horde Leveling Guide
This is without a doubt the best leveling guide available! It features an in-game addon to help you along on each quest. It also gives you the order of quests to do, the location of which quest to do next, and automatically progresses as you complete the quest. It even shows you on the in-game map where to go and what to do. It also covers both Alliance and Horde in one guide. It is a totally in-game guide. Gone are the days of switching windows to read a leveling guide!
Zygor's Announcement of Zygor's Guides 2.0
Joana's 1-70 Horde Leveling Guide
Joana's Famous Leveling Guide. One of the oldest and overall a great guide.
Joana's Video Leveling Guide
This is Joana's Original Video Guide that was posted on the WoW Forums.
Team iDemise Horde Leveling Guide
Recently updated to 1-80, this guide is growing in popularity by leaps and bounds. This leveling guide also features an in-game interface. You never have to alt tab out of the game to look at a guide.