Generation Impact
Youth Service America
Organization that helps US-Americans contribute to their communities through volunteering

YSA's mission is to help all young people find their voice, take action, and make an impact on vital community issues. Although they are a global organization, their services are mostly focussed on the US. They offer the following events, projects and resources:
Financial Grants & Awards*
Training & Resources
Global Youth Service Day
Be Fearless Be Kind Pledge
Semester of Service
Classroom with a Cause
Stories from inspiring youth
Again, for many of the grants you have to, unfortunately, be based in the US. They do have a wide variety of community partners around the globe, though, that may be worth looking into. What I like about their website is their "Knowledge Center" that has a variety of free toolkits (videos and PDF's) in a variety of languages (!) about how to make a difference. If you just have a little bit of experience with global service, you will see that the toolkits are fairly basic and definitely aimed at Western middle-class youth, but you may want to look into it just for ideas and inspiration.