U.S. Treasury Secretary Paulson has endorsed "covered bonds," which are a new idea in the United States but have been used in Europe for centuries, according to this article. Covered bonds are secured by loans carried on the books of the issuing bank. Keeping the loans on the books forces the bank to pay attention to the performance of those loans, unlike the mortgage mess, where mortgages were packaged, re-packaged, and sold until no one really knew how the mortgages were performing.
Covered bonds can be used as an investment vehicle for issuing mortgages, but in Europe, they have been used heavily by the public sector to finance infrastructure, and are backed by the governments receiving the funds. Why are they different than general obligation bonds? Covered bonds enable local governments to tap a much larger, global marketplace of capital funds, meaning more cash could be available for local infrastructure projects at lower rates because of increased competition among lenders.