Most people don't even bother picking up cooking. The 2-10 stamina/spirit buff rewarded from eating a good meal rarely outweighs the trouble of leveling your cooking skill to most players. But there are some recipes that are extremely useful and can turn a huge profit. I recommend leveling your fishing skill along with cooking as many of these require fishing skill to get the materials. Here's a few of the more useful cooking recipes:
Smoked Sagefish: +3 mana every 5 seconds
Savory Deviate Delight: Turns you into a ninja or a pirate for 1 hour
Sagefish Delight: +6 mana every 5 seconds
Dragonbreath Chili: Chance on melee hit: belch flames on an enemy
Grilled Squid: +10 agility
Nightfin Soup: +8 mana every 5 seconds
Poached Sunscale Salmon: +6 health every 5 seconds
Charred Bear Kabobs: +24 Attack Power
Juicy Bear Burger: +14 Damage and Healing
Runn Tum Tuber Surprise: +10 Intellect
Smoked Desert Dumplings: +20 Strength
Outlands Recipes:
Ravager Dog: +40 Attack Power & 20 Spirit
Stormchops: Zap enemies randomly with electricity
Broiled Bloodfin: +8 resist to all schools of magic
Sporeling Snack: Boosts pet's stamina and spirit by 20
Blackened Sporefish: +20 stamina and 8 mana every 5 seconds
Blackened Basilisk: +23 spell damage
Skullfish Soup: +20 spell critical strike rating
Spicy Hot Talbuk: +20 hit rating
Grilled Mudfish: +20 Agility
Poached Bluefish: +23 spell damage
Roasted Clefthoof: +20 strength
Warp Burger: +20 agility
Golden Fish Sticks: +44 Healing
Kibler's Bits: +20 strength & spirit to your pet
Crunchy Serpent: +23 spell damage
Spicy Crawdad: +30 stamina & 20 spirit
Fisherman's Feast: +30 stamina & 20 spirit
Most of these recipes can be sold for very high prices on Auction house to endgame raiders who want that extra stats boost on top of their potions.