Church records have been kept in the Netherlands since the 1500s in some places. The churches kept great records of christenings, marriages, and burials. Then, in 1811, when the French occupied the Netherlands, Napoleon Bonaparte decided to begin civil registration. It was officially instituted a few years later, but some places had started it in 1796. Because of French occupation, the civil registration records from 1811 to 1813 were kept in French, but the rest are in Dutch.
Under the civil registration system, the Dutch were allowed three days to register their vital events with government authorities. Marriages were usually registered on the day the ceremony took place, so the registration date found in the record will be the marriage date, but for births and deaths, that is not the case. Be aware that the first date found when looking at civil registration records for these events will be the date of the registration - you must keep reading to find the date of the actual event.
Both of these important record groups are being made available on various sites. The Internet sites are largely kept up by the city or regional archives that house the records. The Rijksarchiefdienst (National Archive) has a site that contains records from various provinces at www.genlias.nl. Its collection is mainly indexes of town civil registrations from when they began in 1811. The Rotterdam city archive has indexed all the church records up to 1811 for the Rotterdam area along with some civil registrations. This index can be found at http://www.gemeentearchief.rotterdam.nl/. Amsterdam has a site that indexes christenings for 1716 to 1811 in addition to other records at http://gemeentearchief.amsterdam.nl/. One site that has links to digitized records various people have put on the Internet, both on the province and town level, is Genealogische Homepage van Herman de WIT.
If a historical map would be helpful in your research, a site that has some from the 1650s that can be downloaded is http://grid.let.rug.nl/~welling/maps/blaeu.html. Over 1200 images from the Kuijper's Gemeenteatlas from 1868 have been digitized and made available at http://www.kuijsten.de/atlas/index.html.
This is by no means a comprehensive overview of what is available for Dutch records on the Internet. Make sure that you check for online resources whenever you are researching your Dutch ancestors.