Patch 5.1 is live today in the EU and Wowhead have put together a guide of all the new stuff added - go check it out!
Some of the highlights include:
Two new factions offer new gear rewards and mounts while developing the Alliance and Horde conflict in Krasarang Wilds.
Players can permanently increase the ilvl of their gear through currency.
The Brawler's Guild lets players fight challenging solo bosses for vanity rewards and achievements.
Five new scenarios cover the escalating conflict between the Alliance and the Horde.
Many new pets have been added--both wild pets and drops from classic raid bosses. Players can also upgrade the quality of their pets with Battle-Stones.
Wrathion has new legendary quests.
Commendations that increase reputation gains have been added.
Darkmoon Faire and Sunsong Ranch have new rewards and additional perks.
... and many more changes to class and interface.