Crafting Professions
Alchemy
Alchemists gain a bonus called Mixology that grants them extra bonuses when using any flask that they can create. This bonus works out to either +37 Spell Power, +64 Attack Power, +13 Mana per 5, or 320 Health based on the flask. This is a nice buy wow gold bonus if you raid since you will be using flasks all the time. Better yet as an Alchemist your flasks will last twice as long. Also as an alchemist you can make a significant amount of gold by creating flasks.
Best Classes: Any
Worst Classes: None
To really make the most out of Alchemy you really need to be an herbalist as well, which ,cheap ugg boots; limits its appeal. Other combinations work out to be better overall bonuses and if you raid may be better options. This is a great option though for an alt.
Blacksmithing
Blacksmith’s get extra sockets
Blacksmiths get the ability to add two extra gem sockets to their equipment, one to their gloves and one to their bracers. This means that they can further customize their gear as required. This works out to a bonus of +46 Spell Power, +40 Strength, or +60 Stamina due to the extra slots. You could put any number of other bonuses into the slots instead.
Best Classes: Plate wearing classes
Worst Classes: Cloth and Leather wearing classes
The bonuses that being a jewelcraft provide are some of the best and most customizable that there are. In addition you can always pick up uncut gems on the auction house, cut them and resell them for profit.
Leatherworking
Fur Lining Bonuses
Leatherworkers get to fur line their own bracers. This is a leatherworker only item that grants more stats than the equivalent enchant that you could put on your wrist item. This works out to +40 Spell Power, +82 Attack Power, or +62 Stamina over what a normal enchant would grant.
Best Classes: Druids, Hunters, and Rogues
Worst Classes: None
Can be used by any class since the bonus is pretty big, however the best use is with a leather wearing class since they can also make use of the buy wow gold items a leatherworker creates. Leatherworkers can also create cheaper versions of their leg armour kits for themselves which is a nice perk when replacing gear.
Tailoring
Tailors get an interesting option in the form of embroidery. Embroidery puts a proc effect on your cloak that grants big spell power, attack power, or mana regen.
Gathering Professions
Herbalism
Herbalism does not grant a stat bonus, instead it grants a healing ability called Lifebloom. This allows players to be a bit more self sufficient if they are not a healer, or give healers another small healing ability that doesn’t cost any mana.
Best Classes: None
Worst Classes: None
While the heal ability is ok, it is not huge. Many other professions grant much better bonuses. However if you are an Inscriptionest or Alchemest then you probably need to be an herbalist as well, or have an alt that is.
Mining
Extra Stamina from mining
Since you spend so much time mining you earn extra stamina. This ramps up as you level and maxes out at +60 Stamina at level 80.
Best Classes: Tanks
Worst Classes: Any other than tank
Skinning
As a skinner you earn extra critical strike wow gold chance culminating at +40 crit at level 80. This is a good bonus for any DPS class.
Best Classes: DPS
Worst Classes: Healers and Tanks