Updated

The second full weekend of competition at the 2012 Summer Olympics brings with it some of the absolute can't miss events of the London Games, in the water, at the track and on the sand.

Saturday is highlighted with the final Olympic appearance ever from Michael Phelps. He'll swim the butterfly leg in the men's' 4x100m medley relay final, looking to add to his record with career medal No. 22. In track and field, which gets under way in earnest on its second day of events, men's long jump and then men's 10,000m are the must-see competitions.

Then on Sunday, the London Games has its marquee event: Usain Bolt running to defend his gold in the men's 100 meters.

What To Watch at the Olympics, Saturday, August 4:

Track and Field - Men's Long Jump, 8 p.m. ET, NBC (LIVE at 2:55 p.m. ET)

Team USA has two athletes in the finals, Will Claye and Marquise Goodwin (yes, the Texas wide receiver), the latter of which had the fifth-best distance in qualifying.

Swimming - Men's 4x100m Medley Relay, 8 p.m. ET, NBC (LIVE 3:27 p.m. ET)

This is your last chance to see Michael Phelps swim in the Olympics. He'll take the butterfly leg for the United States in the 4x100m medley relay. He'll be joined by Nathan Adrian, Brendan Hansen and Matt Grevers. Good luck, rest of the world -- the last time the U.S. didn't win gold in this event was 1980.

Track and Field - Men's 10,000m, 4:15 p.m. ET, NBC

This is a must-watch because of American Galen Rupp, who is arguably the fastest non-African born runner in the world. He gives the U.S. a real chance at winning its first medal in the event since 1964. He'll be joined by teammates Dathan Ritzenhein and Matthew Tegenkamp, but Rupp's competition will come from the Kenyans and Ethiopians, including defending gold medalist Kenenisa Bekele, and Great Britain's Mo Farah.

Track and Field - Men's 20km Race Walk, 4:45 p.m. ET, MSNBC

Walking, a real Olympic sport, is being tape-delayed, and then aired on MSNBC. That is all.

Beach Volleyball - Misty May-Treanor / Kerri Walsh Jennings

The two-time defending gold medalists will look to advance through the round of 16 (it's live at 4 p.m. ET, but will be likely be saved for NBC's primetime broadcast).

Track and Field - Women's 100m, 8 p.m. ET, NBC (LIVE at 4:55 p.m. ET)

The fastest women in the world will take to the track for the 100 meters on Saturday, with the medal podium likely to be made-up entirely of Americans, including Carmelita Jeter, who turned in the fastest time in the morning's heats (10.83 seconds), and Jamaicans, led by the gold medal winner from Beijing, Shelly-Ann Fraser-Pryce.

What To Watch at the Olympics, Sunday, August 5:

Tennis - Men's Singles Gold Medal Match, Roger Federer vs. Andy Murray, 9 a.m. ET, NBC

Can Andy Murray accomplish what he wasn't able to do at Wimbledon last month?

Gymnastics - Women's Vault, 7 p.m. ET, NBC (LIVE at 9:50 a.m.)

American McKayla Maroney already delivered a memorable valut in the individual all-around -- now she'll try to do it again to win the gold.

Also on the gymnastics schedule for Sunday is men's floor, with American Jacob Dalton competing, and the dumb stupid pommel horse (no one from Team USA qualified, because it is a dumb and stupid event).

Track and Field - Women's 400m, 7 p.m. ET, NBC (LIVE at 4:10 p.m. ET)

The semifinals for the women's 400 meters are being run at 3 p.m. ET on Saturday, and there are three members of Team USA competing for a shot in Sunday's finals: DeeDee Trotter, Francena McCorory and Sanya Richards-Ross, the 2008 bronze medalist. For what it's worth (not much), Botswana's Amantle Montsho, who finished eighth in Beijing, had the fastest time in Friday's heats.

Track and Field - Men's 100m, 7 p.m. ET, NBC (LIVE at 4:50 p.m. ET)

If you only watch one event at the 2012 Summer Olympics, make it the men's 100 meters. Even though it lasts less than 10 seconds, the world's fastest sprinters make this one of the most exciting finals in all of sports. As expected, the three members of Team USA -- Ryan Bailey, Tyson Gay and Justin Gatlin -- and the duo from Jamaica -- Usain Bolt and Yohan Blake -- all advanced to Sunday's semifinals (2:45 p.m. ET).

Can Bolt defend his gold from Beijing? Will Blake beat his countryman, like he did at the World Championships and Jamaica's team trials? Can 30-year-old Gatlin, the 2004 gold medalist, complete his comeback after a four-year ban for doping? Can Gay, one of just three people ever to beat Bolt, win his first Olympic medal?

The story lines, the drama, the speed ... the 100m is can't miss.

For more on the Olympics, check out SB Nation's London 2012 Olympics Hub. For a complete TV schedule, click here.