I apologize in advance if this is a repost, but several searches turned up nothing.
This will take a while, but it is worth the wait.
Here's what you need:
A legitimate WoW account that is being payed for
A Paypal or some other method of payment that is NOT paying for the legit WoW account already (it's a good idea to have it so that it can't be traced back to you)
A second email address
Now, using your legit account, log in to the WoW site and use the "Recruit-A-Friend" option to recruit your second email address. Create a trial account, using the info from the payment source. and wait for it to expire. When it does, use your second payment source to buy a $15 per month subscription (make it so that the billing dates are not the same on the two accounts). Cancel the payment on your second account. Wait 90 days, then using your first account, use the "Scroll of Resurrection" on your second account. Accept it, then pay the $15 for the first month, and cancel it. Lather, rinse, and repeat.
Voila! You are paying $15 for 2 accounts! If you do this on a 30 day rotation (i.e. invite yourself to a new account once per 30 days) then you can have your main account for free while paying the $15 for the alt accounts.
Who this is good for: Scammers, dualboxers (To a lesser extent). Scammers can use this to get a free legit account to scam people with, launder scammed characters, etc. You get your main account and a new legitimate account (where you can use mail, trade, etc.) you can scam and get banned with with no consequence for just the $15, rather than $30.
The only drawback to this is that initially, it takes a while, but after the 90 days, you can have a constant stream of free alt accounts. 1 main account, then 1 free account every month.