Redirect returning users to a certain page?

function redirect_user() {    
        if ( is_user_logged_in() ) {
           wp_redirect( 'http://yoursite.com/page/' );
           exit;
        }
}
add_action( 'init', 'redirect_user' );

This will redirect the user to the page of your choice if they are logged in. It might be necessary to add a conditional that checks to make sure the user isn’t already on that page, to avoid a continuous redirect loop.