Also, talk to your local Rotary, Lions, Kiwanis, and Optimists clubs. They do a lot of international work and have connections overseas. Furthermore, many provide financial assistance to volunteers abroad. When applying to volunteer with an organization, be very specific about the kind of service you can provide them. Many people call me up and say, I just want to help.
Many nonprofit organizations are underfunded, understaffed, and over-worked.
You must prove to the organization that you will be an asset and not a drain by convincing them that you understand their needs and have the skills and ability to truly help them. It is not a wise idea to quit your job with the idea of volunteering right away. Finding a volunteer position overseas takes time. You must be persistent and patient. There is a reason why there is such a long period of time between when you apply, get accepted, and actually join the Peace Corps.