The Boy Scout Roundtable Planning Guide suggests a Public Service feature for January 2012. BSA provides the troop program feature guides as a resource for Boy Scout troops. A PLC can use these guides to plan a series of meetings and outings around a single theme. My post Troop Program Features for Meetings and Outings has more information about these guides.
You can find the plans for the Public Service troop program feature in Volume 3 of Troop Program Features from BSA. The plans include four troop meeting plans and an outdoor program feature which includes a service project.
The focus in this program feature is citizenship and service. Younger Boy Scouts can work on flag etiquette, flag ceremonies, and their rights and duties as US Citizens. Older Scouts could work on the Citizenship in the Community, Citizenship in the Nation, and Citizenship in the World merit badges. Scouts who already have those badges could expand their knowledge by working on Public Health, American Cultures, or American Heritage merit badges.
While the troop program features are aimed at Boy Scouts, the ideas found in there might also be helpful to Cub Scouts and Venturers. These programs also incorporate citizenship and volunteer work, so the leadership could look at the Boy Scout program feature to get some ideas.