Blizzard announced today that the newest expansion for World of Warcraft - Mists of Pandaria will be on sale on September 25th. The announcement can be found on Blizzard's home page for World of Warcraft.

The Standard Edition comes in at $39.99. However, there is also a Deluxe Digital Edition for $59.99 that comes with the Imperial Quilen Flying Mount, a Diablo 3 Banner Sigil and Accent, and Starcraft 2 Battle.net Portraits. It looks like the expansion is available for Pre-Purchase on the World of Warcraft site right now.  

UPDATE: It looks like there will also be a Collector's Edition of Mists of Pandaria, which will retail at $79.99, and includes the following bonuses:

• Behind-the-Scenes DVD and Blu-Ray: Learn about the creation of Pandaria with this two-disc set featuring over an hour of commentary, insider interviews, and developer roundtables.
• Collector’s Edition Soundtrack CD: Experience 20 orchestral pieces from Mists of Pandaria.
• The Art of Mists of Pandaria Book: Explore this 208-page hardcover tome featuring never-before-seen pieces from the expansion, from early concepts to final 3D renderings.
• Chen Stormstout Mouse Pad: Equip your desk with this special-edition mouse pad featuring the legendary pandaren brewmaster.