http://www.squidoo.com/aion-crafting-guide
Alchemy
Alchemy is most useful to Sorcerers and Spiritmasters, since it creates spellbooks and orbs. However, with alchemy you can also create manastones, potions and scrolls which are useful for any class. Being able to craft your own scrolls and potions will save you a ton of kinah. However, leveling up alchemy also takes a lot of kinah, in addition to inventory space. You will be carrying around a lot of gathered herbs, manastones and other materials. While alchemy is no doubt a very useful profession, you might want to level it up later in the game.
Armorsmithing
Armorsmiths produce exactly what you think, armors and shields. Classes such as Templar and Gladiator will have the most use of Armorsmithing, however it's very useful for Priests as well. Since there are basically two ways of obtaining the best armor at high levels, killing bosses or rare monsters, Armorsmithing is a great third alternative for making great armor which undoubtedly helps in both PvE and PvP.
The nice thing about AS is you can make excellent gear for your character every 5 levels, so it's not only an endgame profession. The resources it requires are ore, Aether and most of all money. The downside is, you will not be making huge amounts of kinah with Armorsmithing unless you get really lucky and craft more than one item for the same amount of resources (also called a "proc").
Cooking
I hate to cook, but for some reason I find it interesting in games. Cooking is a fun profession which enables you to create all kinds of temporary buffs which increase your character stats. It's definitely useful, but unfortunately it's nothing you can't get from other players or from the auction hall. Materials for cooking are easy to come by and inexpensive, but you will not be making nearly as much kinah as with some other crafts. It's unfortunate and I suggest you level cooking only for the sake of it. It's not worth your time and money. Hopefully it will improve in the future.
Like alchemy, any class can benefit from cooking.
Handicrafting
Handicrafting produces rings, glasses, staves, bows, earrings and necklaces. This profession is recommended for Rangers and Chanters, but anyone interested in making kinah should consider it. Handicrafting is definitely the best kinah making profession in game. The "procs" are highly profitable, although rare. If you take HC you won't be spending huge amounts of kinah, but you will spend enormous amounts of time gathering the required materials. Wood is not hard to come by, however gems which are required for jewelry are rare and come in small numbers.
Handicrafting is recommended to anyone who has enough patience for gathering materials and interest in making loads of kinah.
Sewing
Sewing allows players to make cloth and leather armor, as well as belts, hats, and some types of shoes. This is a suggested craftskill for Scouts and Mages. If sewing is your choice, don't expect to make a lot of kinah. You will be able to make yourself decent armor and occasionally sell one, but for serious money making I suggest looking elsewhere.
Weaponsmithing
Weaponsmithing is used to create melee weapons such as swords, daggers, polearms, maces and spears. Templars, Gladiators and Assassins will clearly have most use out of this profession and I'd recommend taking it. It works similar to Handicrafting, where the most kinah and best items are made by "procs", so if you don't mind gambling a bit go for it. You can possibly make millions of kinah just for one item which is no doubt a lucrative opportunity for anyone