Some of the new Features for the upcoming expansion are:

• Level cap raised to 90
• A new race: Pandaren
• A new class: Monk
• A Pet Battle System
• Challenge modes for Dungeons
• PVE Scenarios
• A new and improved talent system
• Account wide achievements and mounts
• All new continent: Pandaria
• And many, many more awesome things

The Standard Edition will be $39.99; The Digital Deluxe Edition will be $59.99 and will include:

• The Imperial Quilen Mount
• The Imperial Quilen Cub (Companion Pet)
• Diablo III Banner Sigial and Accent
• Starcraft II portraits

The Collector's Edition will be, I believe, $79.99 or maybe even $99.99 and it will also include:

• Everything from the Digital Deluxe Edition
• "The Art of Mists of Pandaria" a 208 page art book
• A Mists of Pandaria Mouse Pad
• Behind the Scenes DVD and Blu-Ray
• The official soundtrack from Mists of Pandaria

The Standard and Digital Deluxe Editions can be bought at the Blizzard Store as well as your local or online retailers, while the Collector's Edition can only be bought from your local or online retailers.