Brown said sites such as SavvyChavvy and the other seven winning projects have huge potential to influence lives and communities, fighting gang culture and promoting positive images of previously maligned or misunderstood minorities and communities.
"The worst of Britain can always be challenged by the best of Britain," said the PM.
Despite its recent adoption as a term of abuse to stereotype Britain's white working class, 'chavvy' is actually an old Romany word for "youth".
The awards were funded by the Council on Social Action, the National Endowment for Science, Technology and the Arts (Nesta) and the Department for Business, Enterprise & Regulatory Reform.
SavvyChavvy site was one of eight projects honoured in the UK's Catalyst Awards for technologies that are used to serve communities. Other winners included 'virtual nightclub' Wheelies (a club in Second Life for disabled people) and car-sharing scheme, Liftshare.
The 2008 Catalyst winners in full were:
Community Award - SavvyChavvy
David and Goliath Award - Liftshare
Chalk and Cheese Award - FreqOUT!
Enterprise Award - Slivers of Time
Revolutionary Award - Wheelies
Self-Help Award - School of Everything
Individual Hero - Helen Anderson
People's Choice Award - Freeconomy Community