When I built my first website that I was using to promote a few different affiliate products, I was looking for ways to get plenty of visitors to the sites pages.  I started thinking about sites that I visited often to determine what made me go to them.  I realized that I was visiting sites that offered a few casual games more frequently than those that did not.  Once I realized this I started looking for games that I could easily place on my own site.  I found a site that offers all kinds of games so it was easy to choose a few good ones.  I really think this is responsible for getting my visitors to stay around longer.