The best thing to do is to contact the website where your plagerized articles are located and contact the webmaster. Indicate the name and title of the article and the author who plagerized your article. If no action is taken, then contact the web hosting company with and indicate that you have contacted the website owner of the offending article and have had no response. Keep track of dates in which you have communicated to the website owner when you are communicating with the hosting company.

Usually most website owners will cooperate with you, especially if you are polite. Most of these cases are not perpetrated by the website owner, but a member of that website, and they will usually be grateful for the "heads-up" in these cases.