If you used a CC then along with disputing the charge I would have the CC company issue you a new card - if it is not already too late. Same if you used a debit card.
The next place would be the Federal Trade Commission. They really won't do anything but if they get enough complaints they could go after them for wire fraud.
You could try to do a whois on the domain but if they are scammers the info is probably hidden or just plain wrong. Might be worth checking though.
http://www.netsol.com/whois If they are using a virtual server company you could file a complaint with them and they may be able to get you more contact info. They may require a police report or some other documents to release it to you though. This may be why they disappeared. They found out the site was a scam and took it down.