Is possible to trade game items or gold outside of WOW on third party websites?

As a non-WOW player I have wondered: is possible to trade game items or gold outside of the game on third party websites? Does Blizzard have an API or something, or is this kind of activity completely non-sanctioned and takes place in a grey market?

I ask because a friend had thrown out an idea of making an exchange where I could trade World of Warcraft gold for say Second Life currency or Facebook credits, etc. I was wondering if a thing like that was even possible. Sounds like the answer is no.

Thanks!

It's completely non-sanctioned. Blizzard's Terms of Use have the following section:

Ownership/Selling of the Account or Virtual Items.

Blizzard does not recognize the transfer of World of Warcraft Accounts or BNET Accounts (each an “Account”). You may not purchase, sell, gift or trade any Account, or offer to purchase, sell, gift or trade any Account, and any such attempt shall be null and void. Blizzard owns, has licensed, or otherwise has rights to all of the content that appears in the Game. You agree that you have no right or title in or to any such content, including without limitation the virtual goods or currency appearing or originating in the Game, or any other attributes associated with any Account. Blizzard does not recognize any purported transfers of virtual property executed outside of the Game, or the purported sale, gift or trade in the “real world” of anything that appears or originates in the Game. Accordingly, you may not sell in-game items or currency for “real” money, or exchange those items or currency for value outside of the Game.

In other words, trading in-game items for any sort of external reward (be it real money, Second Life money, Facebook credits, or anything else) is prohibited.

COMPLETE EDIT:

Yes. There are two places where you can partake in the auction house out of game:

1.) Blizzard has it's own account addon (~$2/month extra) where you can buy/sell on the auction house out of game.

2.) 3rd party wise, another option (purely observatory) is http://www.wowecon.com/ where you can see the prices of things on the auction house and also view what things have been going for - kinda neat to track patterns of pricing (for instance the weekend inflation that typically happens).

Hope that helps!