Other
Asociaciones, Organizaciones Y Movimientos Juveniles
A great resource from Colombia that connects to various hispanic countries. Youth groups include the Red Cross, Boy Scouts - even rebellious groups!
4-H
National 4 H Council
Learn about local volunteering opportunities for kids of all ages at the National 4-H Council website.
Other
Cdrtcampos: Organizaciones Juveniles
Great site from Cdrtcampos that gives you a number of youth organizations to check out. Human rights, helping refugees, international organizations, you name it.