Construction work continues on the Olympic Park in Stratford, east London
Thousands of people will get an exclusive early look at the London 2012 opening ceremony, Olympics Minister Tessa Jowell has announced.
A total of 2,012 pairs of tickets will be available for the dress rehearsal.
People who volunteer in their communities could get tickets as a reward for giving up their time.
The incentive is part of the national 25th Hour campaign which is based on the idea that people can find an extra hour to make a difference.
Volunteers can go to the 25th Hour website to pledge their time to help out in the regions where they live and work.
Launching the scheme at the Olympic Park in Stratford, east London, Ms Jowell said: "Millions of people want to be involved in the Olympics when it comes.
"This campaign will give them a chance to do that by pledging their time to get involved in their communities and by doing so having the chance to go see the dress rehearsal of the opening ceremony.
A host of national sports organisations, voluntary groups and charities are backing the campaign.
From July 2010, more than 1,000 local organisations will be given the chance to hear how to create volunteering opportunities inspired by the Games, during a series of regional workshops run by Volunteering England and YouthNet.
London 2012 chairman Lord Coe said: "Our vision is to use the power of the Games to inspire lasting change.
"They offer a once-in-a-lifetime opportunity to do something extraordinary, to inspire everyone to use their passion to help others."
London Mayor Boris Johnson said: "Most people don't realise the positive impact one hour can make and the 25th Hour campaign will help the many organisations in the capital and across the country that are looking for people to devote their time, energy and skills."
The 25th Hour campaign is separate to London 2012's volunteer programme which seeks to recruit 70,000 people to help the Games run smoothly.