How do I restrict Internet access to users

Hi,

I would like to restrict Internet access to all the users. I am using windows 2008 server.

We have 10 desktops and 10 laptops. All desktops and few laptops are under a domain in windows 2008.

Is it possible to allow only yahoomail. Also I need to give full Internet access to few people.

If it is not possible with windows 2008 server. Is there any software to accomplish my task.

Thanks
rahsin