Fury of the Sunwell

The glorious fount of arcane energy known as the Sunwell empowered the high elves for millennia, until the death knight Arthas laid siege to the elven kingdom and corrupted its sacred energies. Seeing no other alternative, a band of survivors led by Prince Kael'thas destroyed the ancient fount, and over time the surviving elves fell prey to a crippling magical withdrawal. Now, promising salvation for his people, Kael'thas has returned. Soon the Sunwell will shine once again, but whether the sacred fount will usher in deliverance or destruction remains to be seen. This area includes: * A new quest hub * Magisters' Terrace - a 5-player instance * Sunwell Plateau - a 25-player instance * New badge rewards New Daily Quests: The combined forces of Shattrath have launched an attack on the Isle of Quel'Danas to confront Kael'thas and the Legion at the Sunwell and surrounding areas. Players will now be able to gain reputation with the Shattered Sun Offensive and participate in a new set of daily quests. UI Improvements: The combat log has undergone improvements that allow more robust combat-text filtering, including the ability to define custom colors for enemies and friends, as well as combat text filtering for self and others. Arena Tournament Introduced: Players will be able to create level-70 characters with epic equipment and compete on special tournament realms in a new global arena tournament. For more information, details, and entry requirements, please visit the official tournament pages.

And more - check out the full patch notes.
http://worldofwarcraft.com/patchnotes/