You can play free games online at the blames website.
To play games for free, you computer should come with free games for you to play on them already. If not you can go online and search for the game you want to play and there should be a demo for you to play.
There are many online websites in which you can play games for free. Some of the more popular websites are Facebook.com, Pogo.com, and Worldwinner.com.