Sun 21, shown above, arrived at the North Cove yacht harbor, Battery Park City, on May 8, having begun her somewhat circuitous voyage in Basel, Switzerland, last November. She sailed down the Rhine to the North Sea, around the west coast of Europe and up the Guayaquil River to Seville, Spain, back to the Atlantic and the Canaries, across the ocean to Martinique, up the Antilles to Miami, and up the U.S. east coast to New York. You can see video accounts of her voyage using an interactive map on this site.
The immediate practical significance of this isn't great; much remains to be done to make solar power of the type used on Sun 21 (using solar panels to power electric motors) economical for large commercial vessels. Indeed, the claim that hers is the first "solar powered" crossing of the Atlantic isn't strictly true: since the wind is caused by the sun's heating of the atmosphere, all sailing vessels can be said to be "solar powered". Still, it's an encouraging development.