Feral Druid
As a Feral Druid that wants to level up fast you should specialize in your Cat Form ability because the damage done in Cat Form is better than the Bear Forms available. There are some talents that are better for Bears then for Cats so these can be skipped. Please note that this is a solo leveling build that focuses on maximizing the damage of your Cat Form.
Feral leveling build
Instead of saying why the talents that are chosen are chosen, I will tell you why you can skip the ones that are not:
Feral Instinct: Swipe is a Bear’s ability so you can skip it. The reduced chance to become visible is not important while leveling.
Thick Hide: This talent supports the tanking kind of Druids, not adding anything to quicker leveling.
Brutal Impact: It is more of a Bear ability since it reduces the cooldown of Bash and makes Bash last 1 more second. While for a cat it only gives an additional 1 second to his Pounce stun duration. It’s not bad though so that’s why you can spend a point here.
Natural Reaction: Pure Bear talent.
Primal Tenacity: Not good for leveling purposes since you will remain in Cat Form and fear and Stun effects are not a killer while leveling.
You should add some Restoration talents to this build because of three reasons: Improved Mark of the Wild which is still one of the better buffs out there, Naturalist which increases your damage done by 10%, and finally Omen of Clarity which gives you a chance to use your abilities without spending Energy.
Balance Druid
As a Balance Druid you just try to get as much possible damage but also don’t want to run out of mana too often.
Balance leveling build
Genesis: Isn’t really worth it since Moonfire and Wasp Swarm are the only Dot’s that can be used.
Brambles: Yes, a lot of Entangling Roots can be used while leveling + Thorns, Bark skin and Treants boosted.
Improved Faerie Fire: More something for raids, you don’t want to spend time casting this on a mob.
Both the Feral and Balance talent build focus on maximizing the damage output. Why? Well the answer is simple; you don’t need a lot of survivability because you can heal up from time to time anyway.