Here is a pretty comprehensive list of each profession and what you gain as an added Bonus for a given profession. If you find something missing from the lsit please mention it and I will update the post. Thanks!
Tailoring - Cloak enchants which are superior than the stock enchants everyone else can get are the extra benefit from this profession.
- Embroiders a subtle pattern of light into your cloak, giving you a chance to increase your spell power by 295 for 15 sec when casting a spell.
- 295 spellpower for 15 seconds, with a 35% proc on each spellcast. 60 second iCD. This averages pretty close to ~70 spellpower on the cloak. However you do have to consider that you lose 23 haste from the normal cloak enchant. Depending on stat weights for your specific class this changes the value of the enchant
- Embroiders a magical pattern into your cloak, giving you a chance to restore 400 mana when you cast a spell.
- Appears to have a 35% proc chance and a 60 second iCD giving it a rough value of ~33 MP5
- Embroiders a magical pattern into your cloak, causing your damaging melee and ranged attacks to sometimes increase your attack power by 400 for 15 sec.
- Appears to be a 35% proc chance and a 60 sec iCD giving the proc a value of ~33 AP. This would compare to the 22 agility normal enchant for cloaks, so take that into account when considering this profession.
Alchemy - You have the benefit of flasks lasting twice their normal duration as well as adding a little extra of whichever stat flask you take (64 extra AP, 40 extra Strength, 47 extra SP, etc). You also get the Flask of the North ability, which is a flask usable in arenas that will give you the extra AP/Strength/SP you would get from a flask, since other professions (like jewelcrafting) get to take their bonuses in to the arena, Alchemists should be able to as well. Also consider the Endless Mana Potions and Endless Healing Potions which are not as strong as Runic Mana Potions or Runic Healing Potions, but they are never consumed giving you an endless supply of these potions (these do not disregard the fact that you can only use one per combat, but outside of combat they can help with grinding).
Blacksmithing - Extra socket in your wrists and gloves with a pure red of your stat of choice will net you 80 AP/46 SP/40 Strength/40 Agi/etc. It does not have to be a red gem by any means, you basically gain two gems worth of whatever stats will benefit you the most.
Enchanting - Ring Enchants 40 AP/23 SP/30 Stam, you can put one of these on each ring making total gains 80 AP/46 SP/60 Stam
Inscription - Offers shoulder enchants that are better than the ones you can buy, a breakdown of each is below:
Master's Inscription of the Axe:
Master's Inscription of the Crag:
- Permanently adds 120 attack power and 15 critical strike rating to shoulder armor.
- 80 AP bonus
Master's Inscription of the Pinnacle:
- Permanently adds 70 spell power and 8 mana every 5 sec to shoulder armor.
- 46 SP bonus
Master's Inscription of the Storm:
- Permanently adds 60 dodge rating and 15 defense rating to shoulder armor.
- 40 Dodge rating bonus
Minor Inscription Research
- Permanently adds 70 spell power and 15 critical strike rating to shoulder armor.
- 46 SP bonus
Northrend Inscription Research
- Create random scrolls in an effort to discover new minor glyph recipes.
- Compiles your experiences from the day, creating a random assortment of inscribed works. You are very likely to discover new major glyph recipes this way.
Jewelcrafting - Will grant you the ability to equip 3 of any of the Dragon's Eyes gems below:
- Bold - 34 Strength
- Bright - 68 Attack Power
- Delicate - 34 Agility
- Flashing - 34 Parry rating
- Fractured - 34 Armor Pen
- Precise - 34 Expertise
- Runed - 39 Spellpower
- Subtle - 34 Dodge Rating
- Brilliant - 34 Intellect
- Mystic - 34 Resilience
- Quick - 34 Haste rating
- Rigid - 34 Hit Rating
- Smooth - 34 Crit rating
- Thick - 34 Defense Rating
- Lustrous - 17 MP5
- Solid - 51 Stamina
- Sparkling - 34 Spirit
- Stormy - 43 Spell pen
Leatherworking - Bracer enchants which will grant you a slighlty stronger enchant over the common bracer enchants available to everyone else.
Fur Lining - Arcane Resist:
Fur Lining - Attack Power:
- Permanently enchant bracers to increase your Arcane resistance by 70
Fur Lining - Fire Resist:
- Permanently enchant bracers to increase attack power by 130
Fur Lining - Frost Resist:
- Permanently enchant bracers to increase your Fire resistance by 70
Fur Lining - Nature Resist:
- Permanently enchant bracers to increase your Frost resistance by 70
Fur Lining - Shadow Resist:
- Permanently enchant bracers to increase your Nature resistance by 70
Fur Lining - Spell Power:
- Permanently enchant bracers to increase your Shadow resistance by 70
Fur Lining - Stamina:
- Permanently enchant bracers to increase spell power by 76
- Permanently enchant bracers to increase Stamina by 102
Engineering - Quite a few different possibilities are available for this profession.
- Mind Amplification Dish - +45 Stamina & Mind Control
- Hyperspeed Accelerators - 340 haste for 12s every minute = 68 haste on average
- Reticulated Armor Webbing - +885 Armour
- Hand Mounted Pyro Cannon - 1654 to 2020 Fire Damage Rocket
- Springy Arachnoweave - +27 Spell Power & Parachute
- Flexweave Underlay - +23 Agility & Parachute
- Personal Electromagnetic Pulse Generator - EMP Burst which disrupts Mechanicals
- Frag Belt - Creates a reusable Cobalt Frag Bomb (750 to 1000 Fire Damage & 3 Second Stun every 6 minutes)
- Nitro Boosts - +24 Critical Rating & 5 Second Speed Boost (150% Speed)
Skinning Maxing out skinning and being the appropriate level will offer you the Rank 6 Master of Anatomy ability.
Master of Anatomy:
- Skinning all those dead animals has broadened your anatomical knowledge, increasing your critical strike rating by 40
Mining Maxing out Mining and being the appropriate level will offer you the Rank 6 version of Toughness.
- All your hard work spent mining has made you exceptionally tough, increasing your Stamina by 60.
Herbalism Maxing out herbalism and being the appropriate level will grant you Rank 6 of Lifeblood.
- Uses your skill in Herbalism to absorb energy and nutrients from the earth, healing you for 3600 (increased by maximum health) over 5 sec. Can be used while stealthed or invisible.