This will work, but if you need more flexability and maybe need to post some data, this will allow it. You will need to add a refference to Microsoft Internet Control for it to work.
The problem with this is that it always opens internet explorer, but the beauty is that you can post data, which means you can auto log users into a site
SHDocVw.InternetExplorerClass ie=new SHDocVw.InternetExplorerClass ();
Object vHeaders = null;
Object vPost = wm.PostDataByte;
Object vTarget = null;
Object vFlags = null;
ie.Navigate(wm.PostURL,ref vFlags,ref vTarget,ref vPost,ref vHeaders);
ie.Visible =true;