This may be nuts, but perhaps it isn't. One of the core workhorses of the oil industry are the Very Large Crude Carriers (VLCCs- circa 250,000 deadweight tons) ranging up to Ultra Large Crude Carriers (ULCCs). The ULCCs are not only enormous, but actually the largest ocean going ships in the world. Today's ULCC's are behemoths, typically some 1,300 feet long with a capacity of 500,000 deadweight tons, or more than five times the size of the HMS QM2.
Given the enormous quantity of oil above ground and in storage currently, many of these vessels -- as well as VLCC's -- are idle, or being used as storage vehicles, filled to brim with oil at anchor, at sea for months at a time.
Now just suppose one of these behemoth ships (their replacement value near $200 million) were taken to the site of the oil spill, filled with ballast of stone or whatever and judiciously sunk over the spewing well thereby, given the vessel's size and weight, cutting off the flow of escaping oil, resting there in perpetuity.
Far fetched? Perhaps. But would it not be ironic that one of the major tools of the oil trade served as the solution to the current disaster?