Know Your Lore has covered the benevolent dragons in Warcraft before, but I've decided to highlight a few of them in preparation for Wrath of the Lich King. I feel that saving the best for last is a bunch of crap, so I'm going to start with my personal favorite: Alexstrasza. Admittedly, it isn't terribly hard for her to seal that favorite slot right now. Deathwing and Alexstrasza are the only two Aspects we've been exposed to in a very direct way for a substantial amount of time. To make things even better, she's a headlining character in Wrath.
Alexstrasza is one of five Dragon Aspects chosen and empowered by the Titans prior to their departure from Azeroth. Each of the Aspects was given a domain that they would protect, and have the power to control. Alexstrasza's domain is perhaps the most broad: Life. While all of the Aspects are interconnected and have some sway over one another, Alexstrasza is perhaps the most connected to the others because of her connection to life. Many use this to say she is the 'leader' of the Aspects, but as far as we know, they don't really have one. At least, not until Wrath. Maybe.