InspireMyKids.com is a place where people can find inspiring, age-appropriate, real-life stories, videos and projects to share with the children and teens in their lives to help motivate them to take positive actions and become the best people they can be. There are lots of examples of community service project ideas here, as well as ideas for teachers.

From site:

generationOn is the global youth service movement igniting the power of all kids to make their mark on the world. generationOn has brought the nation’s leading youth service organizations and programs under one umbrella including New York-based Children for Children, The League, Learning to Give, Points of Light Institute’s Kids Care Clubs, HandsOn Schools, and HandsOn Network’s youth-driven programs. By partnering with teachers, parents, schools, community organizations and businesses, generationOn gives kids the opportunity to see firsthand the issues in their communities and the tools and resources they need to respond and become part of the solution.

With the support of a generous investment by the Hasbro Children’s Fund, generationOn is helping young people develop into healthy, empowered, creative problem-solvers and global leaders by experiencing their power and potential through service, service learning and giving back.

YSA offers students, teachers, community organizations, and families the resources and training to help kids find their voice, take action, and make an impact on vital community issues.

There is an impressive collection of resources for teachers to guide your students through each step of planning and implementing a service project.  You can choose from short-term one projects to semester-long projects lasting months.

The National Service Learning Clearinghouse provides lessons, projects, and collaboration groups and discussions to implement service learning projects in your classroom or school. NSLC has an ever-growing database of projects.

Free registration is required for teachers to access training materials and plans.

From site: 

Learning to Give:

• EDUCATES youth about philanthropy, the civil society sector, and the importance of giving their time, talent and treasure for the common good (knowledge),
• DEVELOPS philanthropic behavior and experience (skills), and,
• EMPOWERS youth to take voluntary citizen action for the common good in their classrooms, their lives and their communities (behavior).

Learning to Give educates youth about the importance of philanthropy, the civil society sector, and civic engagement. The Learning to Give Web site offers over 1,200 K-12 lessons and educational resources for teachers, parents, youth workers, faith groups and community leaders free of charge.