Users of the website, which is available free, can become a member and either put themselves forward as a candidate or set up a profile to express views that matter to them, without entering the race to become mayor.
All members then vote for their preferred candidate by scoring their top five issues.
The nominee with the most votes will be announced on March 28 and will receive £60,000 in funding for their deposit and election campaign, giving them strong support against current London Labour mayor Ken Livingstone and Conservative Party hopeful Boris Johnson.
Financial support for the site and for the mayoral candidate has been provided by anonymous members of the public, who believe that the time is right to bring politics back to the people.
The online community was created by a group of friends aiming to "shape the debate, get power back into the hands of the individual and give people a forum for a voice and choice".
David Smuts, one of the founding members and currently a Labour Party member and executive member of the Labour Finance and Industry Group, said: "We're all passionate about something and would probably vote in larger numbers if we felt we had more connection with the issues and with the people who want us to elect them.
"We're calling on Londoners to put themselves forward or to encourage or nominate a friend to stand and help us shape the future of politics through networking and the internet."
Smuts intends to put himself forward as a candidate.