Wowhead has put together a tremendous guide that rounds up all of the big changes coming to Archaeology, WoW's dig-em-and-stick-em secondary profession, in Mists of Pandaria.
Among the big changes are the ability to reset your digsite locations (on a cooldown), teleport to digsites (on a cooldown), and the removal of vendor trash items as rewards.
It sounds like most of the big changes will only affect Archaeology in the new Pandaria zones, rather than retroactively affect all archaeology sites. The article also goes into the new NPC faction associated with Archaeology in Pandaria and lists out a lot of the item rewards you can earn. If you're not afraid of spoilers, you can all the details in Wowhead's preview .