You should learn Cooking, First Aid and Fishing. They can all come in handy. They can get you more currency, and also allow you to regain HP faster. Get all of these up to about 50 or 60 to start out with, at least until you hit lvl 20.
Depending on what class you play, you should mix and match different professions. Right now, I have herbalism trained because it is a good low level profession, and you can make lots of money by selling what you find with it on the auction house. A stack (20x) of Peacebloom goes from 30 to 50 silver on my server.
You might also consider Tailoring. At lower levels, you are better of just making whatever to gain XP in that profession and selling it at a vendor. I normally sell whatever bags I make on the AH, they almost always sell. If you get your tailoring high enough, you can make some prime bucks. Primal Mooncloth bags for example. You have to have 375 (max) level tailoring to make them, but you can get upwards of 200 gold on the AH, but I think the mats are hard to farm.. And you also have to have BC to get them, I think.
I don't know of any other professions. Engineering is fun, but is a b***h to train. If you get it high enough, you can make a cool looking helicopter mount (of course, flying mounts only work in outlands, which is a BC only thing)
If you have any other questions, consult the likeness of http://thottbot.com
. They can really help you.
EDIT-- What level are you and what class are you playing?