The place to go for information about immigrating to Canada, citizenship and other related topics is the Government of Canada's Citizenship and Immigration site.
The site is very large and has a lot of information. Find some of the most-used pages below.
From the Government of Canada: "The only official study guide for the citizenship test is Discover Canada: The Rights and Responsibilities of Citizenship, available from Citizenship and Immigration Canada at no cost. If you have applied for citizenship and are preparing for the citizenship test, your primary resource should be the official study guide. If you use any other material to prepare for the citizenship test, you do so at your own risk."