What do you do when a home loan is "upside down"?

Bought home for 255,000. It is worth 210,000. Should I walk away? I don't feel sorry for my predatory lender. Litton Loans sold my loan to Saxon and Resergent, making it very complicated to deal with two companies. One customer service rep told me it was a bad situation and their company paid "pennies on the dollar" for my loan. I was furious. I am not going to bust my *** to pay these greedy *******. I was in a home buying non-profit program for teachers and they folded two months ago. Everyone told me two years ago (agents, lender) I would sell or refi. Now the adjustable is goin up 300 in February. Yikes! Do I start packing?