Abandoned - but not owned by the bank, or already owned by the bank.
If not owned by the bank yet, your can talk to the neighbors (great resource), post master, police, and can even hire a PI to see where the owners are...this is because you could buy the house from them, as they are still the owners - through a short sale (so you buy at the lower than the current market price or at the market price).
If owned by the bank, you have to see if the property will be sold through the auction or through the REO (listed on MLS) - through realtors. Usually, it's too late by the time the property has been foreclosed upon, to get the bank's attention and buy...
Hope this helps,
Beachfront Realty, Inc.