If you transfred the money with debit/credit card you can claim your money back with the help of the credit card comapny, its called chargeback, i did it few times ! if you need help with that let me know!
FPA Forums Team Note: If you really have some helpful advice on chargebacks, post it publicly. The FPA has had too many people offering help via private messages who turned out to be trying to scam victims a second time.
if you transferred the money with wire the only thing that you can do is take them to court only if you know that real location and real name of the owner...