If you are a Permanent Resident you can sponser family members (which includes spouses) to Canada. Check out the Canada Immigration website at Citizenship and Immigration Canada | Citoyennet? et Immigration Canada You will be able to find all your answers there or if not, there are toll free numbers you can call.
If you are wanting to sponser a fiance, I think that would be very hard to do as Canada doesn't have a Fiance visa like they have in the US.
If you are married and can prove that it is legal in Canada and have documentation backing up your relationship then you should be able to.
Yes you can be a sponsor if you have permanent residency in Canada. As Lexi said Canada does not have a fianc? visa but there are other options besides marriage.
