The first part of the Cataclysm prologue just started on live servers. Alliance player will find the Operation Gnomeregan event in Dun Morogh and Horde players should go to Durotar for Zalazane's fall.

This is a very fun questline, it's not too long and it's a pretty nice introduction to what will happen in Cataclysm! For more details on the quests please read HERE on MMO-Champion