Can't Afford Shortfall

The best option is probably to stay put, don't sell, and wait however long it takes for the market to recover ad your equity to grow.  That won't work, of course, for someone who absolutely must sell for job or health reasons.
If you must move, there's always the option of renting the place out, but that has lots of drawbacks.  If you're moving out of town, being an absentee landlord is asking for real problems.  In some areas, you can't expect enough rental income to cover your expenses.  And when you eventually do go to sell, a place never looks as good, after being rented out, as it did while you were living there yourself.
Of course you can always try talking with your mortgage company about whether they have an suggestions.  Sometimes they're willing to work something out.  They're probably overwhelmed with requests right now, though, so be prepared for some frustration.
Don't be so fast to reject a short sale.  One in which the lender agrees to cancel the remaining debt is a pretty good deal and anyone who absolutely must sell may be lucky to have it offered.