Also, make sure you check on the tax implications of walking away from your mortgage. You could be stuck with owing taxes on the forgiven debt.
I saw this mess coming and started trying to sell our too-large house back in 2007. I also saw the end of my marriage coming up fast, and intertwined the planning. I slashed the price as much as I could and got out while the getting was doable, even though I had to bring a check for $5k to closing. I have been renting ever since, and have been thankful for the mobility. The guy who bought the house from me suffered some bad fortune, and has been unable to sell it for 18 months now (it's been empty all that time) - at 20% less than he paid for it.
This is not true when we short sale and had 50K in forgiven money you donot have to claim that. This was in turbotax.
Here is the article Home Foreclosure and Debt Cancellation