This was clipped from an article at gather.com. It outlines the potential of using Zygors 1 to 70 Alliance and Horde Guide for World of Warcraft.

The site is spot on, showing how Zygor Guides is second to none when it comes to leveling your WOW character to level 70 in supersonic time.

So why is it that this site rates Zygors Guide above the rest ? Well it's quite obvious when you read through and you have used others. As the article suggests, other guides you have to Alt-tab out of the game to read, which when you add up over the period of leveling 1 to 70 is a huge chunk of possible game play and other guides that are in-game, meaning you can utilise whilst still playing, don't start untill you reach a certain level.
Zygors 1 to 70 Alliance and Horde Guide is different with respect that it covers every race, class and starting zone. You are never limited with your descision as to what you want to play, since whatever class you are, your still going to rocket through the level