Usually neighbors can be a pretty good resource for situations like these. Generally there is someone that is keeping an eye on things for the owner. Someone may be able to provide you with the contact information you need.
In this market my first guess would be a vacant home with no sign is a property going through foreclosure and will soon be for sale. The court house in the proper county will have owner information however it will not likely have a forwarding address for the owner if they have moved. If you are really agressive you might knock on the neighbors door. They may be your best source of information. You might get lucky and find them in whitepages.com Good luck and happy hunting.