Chris Hoy won gold for Britain, Michael Phelps triumphed again and Haile Gebrselassie waved goodbye to the track on a busy day of action in Athens.
Hoy set the fastest time ever seen at sea level
Hoy smashed the Olympic record in the men's cycling 1km time trial to beat Arnaud Tournant of France and grab Team GB's second gold of the Games.
Meanwhile, Kenenisa Bekele won gold in the men's 10,000m final, with distance running legend Gebrselassie fifth in his final track appearance.
And Phelps won his fifth swimming gold in the 100m butterfly on Friday in an Olympic record of 51.25 seconds.
In the velodrome, Hoy powered round the track in a time of one minute 0.711 seconds - the fastest time ever at sea level.
It was a nail-biting end to an extraordinary session of cycling which saw the Olympic record lowered four times.
In the pool, Phelps produced a brilliant finish to edge out team-mate Ian Crocker by 0.04 seconds. It took the teenager's individual medal tally at Athens to seven - five golds and two bronzes - but the American will not swim the final of the 4x100m medley relay.
However, Phelps will still get a medal if the US team are successful as he competed in the heats.
Compatriot Gary Hall triumphed in a blanket finish to the men's 50m freestyle, winning in 22.93 seconds.
Kirsty Coventry of Zimbabwe won gold in the women's 200m backstroke, with Britain's Katy Sexton finishing seventh.
Meanwhile Ai Shibata won gold for Japan in an exciting women's 800m freestyle.
But Alison Sheppard was squeezed out in the semi-finals of the women's 50m freestyle, with Inge De Bruijn of the Netherlands fastest of the qualifiers.
Grant Hackett is the overwhelming favourite for Saturday's 1500m, despite Britain's David Davies setting the fastest qualifying time in a British record.
In the first big track final of the Games, Bekele produced a devastating finish to win the 10,000m in a new Olympic record time of 27:05.11.
Distance running legend Haile Gebrselassie was unable to defend his title, finishing fifth. It was his final track appearance, as he will now concentrate on the marathon.
The heptathlon also began on Friday with defending heptathlon champion Denise Lewis in action for Britain - but it was compatriot Kelly Sotherton who impressed.
The Isle of Wight athlete produced a personal best in the high jump and was second after day one on 3869 points, behind Sweden's red-hot favourite Carolina Kluft.
But there was bad news for British sprinter Darren Campbell, who revealed on Friday he is suffering with a slight hamstring tear.
Kelly Holmes ran a perfect race to qualify for the semi-finals of the 800m by winning her heat.
Hicham El Guerrouj was among the top names in action, the Moroccan legend cruising through to the 1500m semi-finals, along with Britain's Michael East.
Britain's Abi Oyepitan finished third in her second round 100m heat to qualify for the semi-final, while Gail Devers only went through as a fastest runner-up.
Phillips Idowu, booked his place in the final of the triple jump reaching 17.33 metres, and Tim Benjamin reached the semis of the men's 400m - but Daniel Caines and Malachi Davies both crashed out.
The first athletics gold of the day went to Italy's Ivano Brugnetti in the men's 20km walk.
And Team GB enjoyed a bright start to day seven with Campbell Walsh taking silver in a dramatic K1 kayaking final.
Walsh had been third but was moved up a place when Frenchman Fabien Lefevre was given a delayed two-second penalty.
In the velodrome, Britain's Bradley Wiggins won through to the final of the men's 4km individual pursuit where he will face Australia's Bradley McGee on Saturday's final. Team-mate Rob Hayles will race for bronze.
Victoria Pendleton finished sixth in the women's 500m cycling time trial after setting a British record of 34.626 seconds, with Australian Anna Meares winning gold in a world record time.
Amir Khan lived up to his bright reputation by easily beating European champion Dimitar Stilianov with a superb display in the lightweight boxing.
The spectre of drugs once again cast its shadow over the Games with the news that Indian weightlifter Sanamacha Chanu and Uzbekistan's shot putter Olga Shchukina had been disqualified by the International Olympic Committee after positive tests.
Meanwhile, the Greek team confirmed that one of their athletes, believed to be wieghtlifter Leonidas Sampanis had tested positive for a banned substance.
In tennis, Nicolas Massu of Chile will play Mardy Fish for the gold medal in the men's singles, as the South American aims to become Chile's first-ever Olympic gold medallist.
Japan's Maki Tsukada captured gold in the over-78kg women's judo competition, beating Cuba's Dayma Beltran - who had accounted for Britain's Karina Bryant.
And Chris Draper and Simon Hiscocks are in with a chance of a medal in the sailing 49er class, although the pair slipped from third to fourth.
British Olympic Association chairman Craig Reedie said he was delighted by Friday's displays, adding that Hoy's gold would give Matthew Pinsent and his rowing team-mates a huge lift ahead of their final on Saturday morning.
"There's a huge knock-on effect. The BBC feed goes into the rowing team headquarters and the reaction up there can do nothing but good for Saturday morning," he said.
"With Campbell Walsh coming within a fraction of a gold and young boxer Amir Khan beating the European champion, it's been a really good day.
"It was a marvellous ride. It's tough coming into this competition as the reigning world
champion and I'm so pleased for Chris."