Shadowmoon valley has a number of important quest lines with good rewards such as:
The Cipher of Damnation
and The Warden's Cage Questline
both visible here: http://wowwiki.wikia.com/wiki/Shadowmoon_Valley_quests
The Frostwyrm Lair has been released! Make your way to Kel'Thuzad's dark chamber and put an end to the master of Naxxramas. Good luck adventurers!