International volunteer opportunities for students (age 14 yrs to 22 yrs) are of two kinds. Personally paid volunteer travel programs or UN, other agencies paying for you. To get a free UN volunteering opportunity is not very likely because of the volume of the applicants and also time commitment (min 6 months or so). I’ll recommend GVI-Canada for a paid volunteer- travel program (IVHQ and Volunteer forever and many more links are below). These paid programs enhance students resume for future job prospects at UN, Intl. Development or local governments.
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Global Vision International is a paid volunteer travel program. Endorsed by many international charities and also universities. (NYU).
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IVHQ -very budget friendly program.
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Volunteer forever is an excellent resource site for volunteer abroad programs. Pls see 925 programs they have on their website.
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Volunteer Service Overseas. International program (Free).
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UNV-United Nations Volunteer Program (Free).
Domestic-Canadian Volunteer Opportunities
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Charity Village is the biggest Canadian volunteer resource site. Most non profits use their services for advertising volunteer opportunities.