Dana Vollmer is another swimming star who shone for America in the 2012 London Olympics. And though you may not believe it, her swimming career goes back as far as 2001, when she won a bronze medal at the Goodwill Games in Brisbane (in the 4x100-meter medley). The Goodwill Games are done, but Dana Vollmer is still here. :-)
At the 2012 Olympics, she earned gold medals in the women's 100-meter butterfly, 4x100-meter medley relay, and 4x200-meter freestyle relay swim races. She also has a gold medal from the 2004 Athens Olympics, won in the 4x200-meter freestyle relay. This is the only Olympic race Dana Vollmer has won twice, but don't fret - she holds the world record in the 100-meter butterfly. :-)
She also competed in the 2003 Pan American Games (an Olympiad for Western Hemisphere nations, though it never seems to be on American television) in Santo Domingo, where she won gold in the 200-meter freestyle, the 4x200-meter freestyle relay, and the 4x100-meter medley. She's also won medals of varying colors in several championships.