Northern Stranglethorn is a new zone in Cataclysm since old Stranglethorn Vale was split in half after the Sundering. The land just south of Grom’gol Base Camp has collapsed into a large whirlpool.
Nesingwary’s Expedition is now a large encampment while the Venture Company Base Camp has been deforested. The large vortex on the border between Northern Stranglethorn and Cape of Stranglethorn is known as the Sundering. Be careful though, it’s nothing like the Maw of the Void.
Players can also learn about the political changes to Zul’Gurub which includes rescuing a cute Lashtail Hatchling after u kill Bloodlord Mandokir. Just look for the exclamation mark for An Old Friend once you’ve killed him (to the right of where Mandokir normally stands). Note that only one person per lockout can complete the quest assuming you’ve done the pre-chain.
You can also get involved in Nesingwary’s expanded hunting operations as well as check out the changes to Yojamba Isle where the majority of structures have been removed.