Always worth reading...and keeping in mind! 
"Volunteerism has common roots, but manifests itself with enormous diversity. This ranges from the highly organized operations of the Red Cross and Red Crescent Societies around the world aimed at improving the conditions of vulnerable people by mobilizing the power of humanity, to the self-help voluntary activities of community burial societies in rural Zambia. However, some key universal principles of volunteerism emerge from this diversity."
Read UNDP Essentials No. 12 on Volunteerism & Development (PDF files):
Spanish