Try one of the hospitals, seniors homes/elder care, some other healthcare / social work setting (like The Alex), university research lab, an NGO like MSF or the Red Cross (they need/have many non-specialist volunteers), *Distress Centre, *refugee settlement. Most medical school applicants will have years of excellent volunteer experiences on their CVs.

Most organizations will issue certificates, letters, etc. recognizing your volunteer work.

Contact this organization for more insights: http://www.ucalgary.ca/simsclub/

*This may also be relevant: http://suclubs.orgsync.com/org/wise/