I just finished the Wrath Gate quest line in Dragonblight and it was easily the most amazing and intense experience I’ve ever had in World of Warcraft. I did the Alliance version and I can’t wait to do the Horde version on my Blood Elf toon. It’s amazing, if you do nothing else in WoTLK, do this chain. I’m still a little emotional over it.
Btw, The cut scene is up on YouTube for those out there who want to horribly spoil themselves, just search for Battle of Angrathar the Wrath Gate.
Fricka's Flights of Fancy 
I’ve been hearing about this and really can’t wait to do this on my priest. The levelling is going slowly as I level with my boyfriend’s 68 DK, but hopefully we’ll be there soon enough.
I picked up the start of the chain at lvl 72 so at least it doesn’t require waiting until 80… I’m leveling so slowly it would be weeks before I even come close to 80.