Canada Revenue Agency:

http://www.cra-arc.gc.ca/menu-e.html

Associations:

Chartered Accountants of Canada
http://www.cica.ca/

Chartered Accountants of Ontario
http://www.icao.on.ca/

Canadian Tax Foundation
http://www.ctf.ca/

Tax Planning References:

Taxtips
http://www.taxtips.ca/

Canada Tax Sites
http://www.taxsites.com/international/canada.html

CICA The Personal Tax Planner Guide
http://www.cica.ca/index.cfm/ci_id/8782/la_id/1

Vendors of Tax Products:

CCH
www.cch.com

Intuit
www.intuit.ca

Taxprep
http://www.taxprep.com/