The White House Open Government Initiative is a really big deal along these lines, much bigger than people know.
We're also seeing remarkable innovations across the country, like in Manor, Texas.
There's a guy leading remarkable stuff there, Dustin Haisler, who takes a good look at some of the software for such purposes:
Specific-Task Motivated Idea Platforms
These platforms (like Ideascale, Uservoice, etc.) are great a gathering ideas for a specific purpose. For instance, many online voting challenges have adopted these platforms to gather votes for a set period of time. After a user expends their vote or votes they are no longer motivated to return to the platform aside from seeing what ideas are on top.
Structured-Idea Collection Platforms
This type of platform (like Spigit) collects and manages ideas on a board scale within multiple departments of an agency. Unlike the Specific-Task Motivated Platforms, users are free to submit ideas at any time within multiple departments. Since users are not motivated by specific-tasks, they must be motivated by a game-mechanics (ranking & rewarding of actions). In this type of platform, ideas are driven by the participants through an idea funnel.