The two options I know of that you have involve either a short sale, or a government assistance program.
In the last couple years there were a few government programs established to help those who were underwater, but usually only if you only had one house(intention was to be no help to the irresponsible who bought up secondary properties during the bubble and contributed to the bubble).
One such program was the Hardest-Hit Fund, but was offered to only a few states effected the most by the housing crash. In Florida the program was managed by FHFC, but those eligible were reached out to from lenders. It was kind of unfortunate that it was done this way, because you could fall through the cracks based on the diligence of the particular company or poorly defined eligibility criteria. You pretty much had no power to initiate the process on your own.
Each states used the funds in different ways. Among them, either assisting the refinancing the existing mortgage(which is what you seem to want to do), or helping cover the difference for a short sale so that the home owner could move into more affordable housing.
Here is an example of exactly what you are trying to do, which is reduce your principal:
If you contact your state's housing agency, they might be able to tell you if there is any assistance possibly available for you. I do not know how other states structure their housing agency, but Florida's has a single-family division of their agency that would deal with such inquiries.
If you are willing to part with the existing home and find one of equivalent value, then a short sale might be an option.
You would sell the home for what it is worth, the bank would need to approve the short sale and take a loss, and you would basically walk away with nothing in pocket. This means you will have to furnish your own down payment for a new home.
Then you could look for a $150K home and purchase that home, and thus your goal of living in a $150K valued home with a $150K mortgage would be obtained.
However, such sales are sometimes difficult as it can take a couple months for the bank to approve the sale(if at all). Depending on your mortgage, the bank may be able to actually turn around and sue you for their loss, even though they approved the short sale. So you would certainly want to consult with a professional before pursuing this option.
Disclaimer: I do not know how either of these options will effect your credit. The former is likely to effect it little, the latter is likely to effect it negatively(to the extent of "completely destroying" I do not know).