The 1891 Canadian Census is fully online now at the Library and Archives Canada (LAC) www.collectionscanada.gc.ca/databases/census-1891/index-e.html.
The 1891 Census was taken in Prince Edward Island, Nova Scotia, New Brunswick, Quebec, Ontario, Manitoba, and the Northwest Territories (which, at the time, covered modern-day Alberta, Saskatchewan, Northern Manitoba, Northern Ontario, Northern Quebec, Labrador, Yukon, Northwest Territories, and Nunavut).
The census was taken on April 5th, 1891, and very little change was made to the collection of the data from previous censuses. Information was gathered for 4,833,329 individuals in 1891.
Unfortunately, only Schedule I remains (a nominal list of the people in the country) - all of the other schedules (there were 8) were destroyed - and only Schedule I was microfilmed.
There are 25 columns, and you can read their definitions and explanations at www.collectionscanada.gc.ca/databases/census-1891/001081-2000-e.html.
There are three things which struck me about this census, and I think they are really good - it's free; you get to view the complete image of Schedule I; and you can add a comment, if you wish.
Congratulations and "Thank yous" go out to the LAC and to Ancestry.ca for this much-anticipated release.