https://www.youtube.com/watch?v=lhBGNJQvbUo
http://www.jocys.com/software#Text_to_Speech
Note: this isn't my addon, I'm just a fanboy passing along a new paradigm
Every year or so a truly monumental addon comes along that fundamentally improves/changes the way we play, such as Power Auras, Weakauras, Battleground Targets, GladiatorLOSSA, Oqeue, VEM.
Jocy's Text to Speech is the latest to join this pantheon of awesomeness. It reads in a natural voice (male, female, robotic etc) quest text and NPC gossip. Questing is actually fun again, I can hear quest text read to me in a natural voice whilst I'm going from one place to another. Text that would normally be ignored. So this addon saves a huge chunk of work that Blizzard did, and adds meaning and fun to an otherwise laborious task.
The latest patch will play the quest even after closing the window, making for a seamless experience.
Make sure you get the real-sounding voices at Ivona as well, as the ones shipped with Windows 7 and 8 are shite. You can try before you buy. These will greatly improve your overall computer experience as well (not just WOW) on programs such as Ventrilo.
As speech recognition improves, this will undoubtedly become part of WOW. I can see in the future this having extra options for raid chat, and NPCs that you are passing in the world.