British Airways, Eurostar and Adidas are among the London 2012 sponsorship brands leading the charge hosting special one-off events.
BA is flying an Airbus A318 over the Olympic Park today at 1pm to mark the countdown.
The plane had the "one year to go" slogan inscribed on its belly (see the video above including Olympic gold medallist Kelly Holmes), which will be visible from the ground when the aircraft is flying.
Eurostar has today (Wednesday) teamed up with London 2012 chairman Seb Coe in welcoming hundreds of European Olympic fans and athletes to London marking one year to go.
Coe and other famous former athletes, such as Colin Jackson, are having their footprints cast in clay at St Pancras International station, marking the first steps on the way to London 2012.
Eurostar is the official rail service provider for the games and will be hoping for a big bounce in sales from its sponsorship of the Olympics.
Adidas has brought together global music icons Snoop Dogg, Warren G and triple jumper Philips Idowu in a three on three basketball match against members of GB Basketball to celebrate the occasion.
London 2012 sponsors are also running ads today across the national press, as they look to capitalise on their sponsorship.
These include Holiday Inn, which is offering 50% off hotels stays booked today; Samsung which is running an ad campaign starring David Beckham to promote its search for Olympic torchbearers for the opening ceremony; and Lloyds TSB which is focusing on how the games will impact its business.
Coca-Cola, McDonald's, Procter & Gamble, BP and Visa are among the other official Olympic sponsors for 2012.
All have used the Olympics 2012 as a key part of their marketing strategy during the run up to the event.
For a round-up of the marketing activity linked to the Olympics to date, visit our Olympics 2012 news page.