Cross-Realm raid browser now has new categories for Mists of Pandaria World Bosses (Celestials and Ordos)
and Flexible raid difficulty for Siege of Orgrimmar.
The cross-realm raid browser is accessed through the 'Social Pane' (bound to the O key by default) and look for the 'Raid' tab on the bottom right.
From there you can set the character as looking to join a raid or browse players that are forming up for a raid.
For more information on this change,
please see the thread titled Cross-Realm Raid Browser on the PTR Discussion forum.
Players are now able to place raid markers in the world even while dead.