Google Adsense also known as an Ad Server will deliver ads to your site and pay you. This a great way to supplement income. It won’t pay for that new BMW (it may if you are large enough) but still could easily cover the cost of the commercial hosting or your annual SSL security certificate.
Whats so unique about Google adsence is that google will actually reads the page it is embedded on and deliver pertinent ads. For instance, if you have a car website such as stevescars.com and you wrote an article regarding Auto Transporting, google adsense will read that and deliver relevant ads regarding auto transporting.
see example: http://stevescars.com/auto-shipping/ (left margin skyscraper Ad )
For more information go to Google Adsense