A list of things you can do in Mount Hyjal.
Explore Hyjal - Explore the named locations in Hyjal. A map can be found here, or you can get the Tom Tom coordinates from this comment. Contributes to the meta-achievements Explore Cataclysm and World Explorer.
Coming Down the Mountain - Complete 115 quests in the zone. Contributes to the meta-achievement Loremaster of Cataclysm.
Beware of the 'Unbeatable?' Pterodactyl - Complete the quest chain that ends with Egg Wave. It starts with The Hatchery Must Burn.
Bounce - Bounce 20 times on the trampoline at the Whistling Grove. People are currently reporting that if you complete the quest Aessina's Miracle, you will get phased and become unable to jump more than once consecutively. If you haven't finished the zone yet, be sure to grab this before you do. If you are already done, this has been confirmed as a bug and is being looked into.
[Heroic] Blackrock Caverns - completed upon killing Ascendant Lord Obsidius. The heroic counts towards the metas Cataclysm Dungeon Hero and Defender of a Shattered World, and a guild group will earn credit for the Guild Cataclysm Dungeon Hero.
Crushing Bones and Cracking Skulls - Use Bonecrusher's Skullcracker ability to kill 10 angered earth elementals.
* He casts Skullcracker at 66% and 33%.The adds he needs to kill are summoned regularly via an earthquake he casts. You do not need to kill all 10 at once. Avoid AOE on them, and when he casts Skullcracker they will also be pulled to him. You can use stuns and roots to keep them in place for Skullcracker, or have the tank keep them in range of the boss.
Too Hot to Handle - Kill Steelbender after he has 15 gained stacks of Superheated Quicksilver Armor. It's been noted that he doesn't have to die while having 15 stacks, but rather must reach 15 at some point during the fight.
* My tank did this without letting me know, but it wasn't much of a problem. He gradually brought Steelbender in and out of the fire, gaining stacks slowly without letting them drop off. Since we were in vent, I was able to call out when he should let the stacks decrease so I could patch up the group before the healing got too intense.
Arrested Development - Let Corla's 3 adds evolve, kill them, then finish her.
* Let them evolve one at a time. If you have an offtank, keep the add 40yds away from Corla to avoid Aura of Acceleration. Make use of interrupts to prevent Shadow Strike and fear. Use cooldowns liberally to ensure that the adds die quickly and the tank stays topped up.
Ascendant Descending - Kill Obsidius without any party member getting 4 stacks of Crepuscular Veil, which is channeled by his three Shadows of Obsidius.
* The channel begins in melee range, so the adds must be kited, slowed, rooted, and stunned if possible. In melee range, 4 stacks takes about 5 seconds, but the debuff resets quickly if not being applied. Remember that Obsidius changes places with adds at 66% and 33%, so aggro on the new add must be reacquired.
To All the Squirrels Who Cared for Me - Alpine Chipmunk, Grotto Vole, and Rock Viper can be found in this zone.
The Guardians of Hyjal - you can get to 6220 Revered via quests (beginning at 0 Neutral and earning 27220 rep unbuffed). Provisioner Whitecloud can be found at 62.8,23.9 in Nordrassil.
You can EITHER a Gold Mini Jouster OR a Blue Mini Jouster from the quest Egg Wave. The chain starts with The Hatchery Must Burn.
There are no obtainable mounts in this zone.
You can fish Mountain Trout from pools and open water. Striped Lurker and Sharptooth are fished from open water. These will count towards the meta achievement The Limnologist.
You can acquire the following fish/meat for their accompanying recipe to get credit towards The Cataclysmic Gourmet. The number in parentheses is the total amount you will need to cook one of each recipe.
Basilisk "Liver" (1) - Basilisk Liverdog
Toughened Flesh (1) - Blackened Surprise
Dragon Flank (7) - Broiled Dragon Feast, Grilled Dragon
Delicate Wing (5) - Broiled Dragon Feast, Feathered Lure
Mountain Trout (1) - Broiled Mountain Trout,
Striped Lurker (2) - Lightly Fried Lurker, Lurker Lunch
Sharptooth (3) - Fish Fry