At the Aquatics Centre: On the final night for swimming, Dana Vollmer and her relay mates try to duplicate their gold medal finish, this time in the 4x100 medley relay. And Michael Phelps calls it a career with the men's 4x100 medley relay. He'll retire as the most decorated Olympic athlete ever, going into the race with 21 career medals (17 golds).At the Olympic Stadium: They'll be off and running in track. Medals will be awarded in the women's 100 meters, featuring Carmelita Jeter and Allyson Felix of the U.S., and the prelims of the men's 100 will be run. Four of the fastest sprinters in history -- Usain Bolt, Asafa Powell and Yohan Blake of Jamaica and Tyson Gay of the U.S. -- will race for a spot in Sunday's gold medal showdown. Medals also will be awarded in the heptathlon, the women's discus, men's long jump, the men's 20K race walk and the men's 10,000 meters. At the Basketball Arena: The U.S. men's team sent a message to the rest of the teams in the tournament with a record-setting 156-73 win against Nigeria on Thursday. Next up? Lithuania, which has two Toronto Raptors on its roster -- forward Linas Kleiza and center Jonas Valanciunas. At the All England Club: Reigning Wimbledon champion Serena Williams gets a chance to add a gold medal to her tennis résumé when she plays Maria Sharapova of Russia in the final. The Bryan brothers, Mike and Bob, go for the gold against France's Michael Llodra and Jo-Wilfried Tsonga in the men's doubles final.