Here are the three best resources I have found on the web that address the legal issues organizations in Canada should be aware of when engaging volunteers:

1. "Volunteers and The Law" (April 2007), prepared by David Stout and Loreen Irvine, lawyers at Nelligan O'Brien Payne in Ottawa;
2. "Volunteers & the law: A guide for volunteers, organizations and boards" (2000), prepared the People's Law School; and
3. "Volunteers" Employment Standards fact sheet, Government of Manitoba.