What recourse does a seller have when a buyer backs out of a signed real estate sale?

In the US, depending on the circumstances, the seller may be entitled to keep the buyers' deposit if the buyers agree or they take the buyers to court and win their case. (The listing company is not allowed to disburse the deposit unilaterally). Usually, sellers are better off just putting the house back on the market and dealing with the inconvenience.

If the buyer defaults and it causes major complications for the seller in a market that is depressed, the seller can also sue the buyer for Specific Performance. This would have the court step in and force the buyer to complete the transaction.