From the about page:
What is Budget Ballot? Budget Ballot is a tool that Councils can use to run Community Budgets. A Community Budget is a pot of money allocated for use in a particular area or community. Members of the community can then submit ideas for how this money is spent, and then vote on which they want to make happen.
About the project: Budget Ballot was created by thinkpublic as part of NESTA’s Your Local Budget programme. It was designed by Ivo Gormley and Joseph Smith and developed by Rob McKinnon and Matt Andrews with support and guidance from Izwe, DxW, and Ian Drysdale.
As of November 2011, Budget Ballot is in beta.
Update: Budget Ballot has been discontinued. In order to access the site, view an archived copy.