A Kickstarter where micro-projects (projects of less than $20k), seeded from the backlogs of City agencies, are published.
Civic Hackers, Students, Researchers, Independent contractors can then "bid" on these projects.
This not only saves money (the traditional RFP process introduces too much overhead and automatically eliminates people who are not familiar with it), it also seeds the Civic Innovation ecosystem.
In addition, citizens and local residents can also publish their own BigIdeas for CivicApps ala the existing Kickstarter and even add to the kitty of existing projects.
All resulting work is then published on a Civic Github. And maybe, taking a page from the Quirky biz-model, people who contribute to the project get a "cut" of the kitty, proportionate to the work they've contributed.