Parish registers can also also be accessed on FamilySearch.org (here). These records do not require a subscription, but are not fully indexed, so you will have to know the place and date when the baptism, marriage or burial took place in order to find the record. This collection also only goes up to 1900, so you will need to go to ancestry.com for later dates.
Both collections cover very similar territory, but don't assume that they are identical. Take the marriage record for my 6th great grandparents, Jean Baptiste Halé and Véronique Paradis, who were married in Lauzon on April 12, 1779. The quality of the digital images in this case differs considerably.
d'Augustin halé pere de L'EpouxThe second image makes it much easier to identify the name of the groom's father.
of Augustin Halé father of the husband
A final resource that can be very helpful in navigating these records is the PRDH which has a database called Repertory of vital events which covers many of the same records during the period from 1621 to 1799. The records in the database are extracts, not originals. The main advantage of this site is the standardization of surnames which makes it easier to search the records than at ancestry.com where you not only have to deal with numerous variants, but many poor transcriptions. You simply plug a variant into the name standardization tool and then use the standardized surname to perform your searches. Another advantage is the inclusion of marriage contracts from notarial records when the marriage was absent or incomplete in parish records and also the inclusion of a variety of other records. For a more complete description of the database go here. These records are available through a subscription.