First, you can (and should) contact your lender(s) to discuss a loan modification.  This is a process by which they can change the terms of your loan to obtain a reduction in the monthly payment making it easier for you to stay in the house while waiting for the market to improve and help you recover at least some of your lost equity.

Second, you can just stop making your loan payments and wait for the lender(s) to start the foreclosure process.  This process usually leads to extensive damage to your credit and can make it difficult or impossible to qualify to purchase a new home for as much as 10 years.  If a “Notice of Default” has already been filed against your house the foreclosure process has begun, but it can often be delayed or suspended if you take the proper steps quickly.  You can also consider a “Deed in Lieu of Foreclosure” with the lender to shorten the process but your credit report will still show an unpaid mortgage debt.